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BackgroundThe intergenerational transmission of obesity-related traits could propagate an accelerating cycle of obesity, if parental adiposity causally influences offspring adiposity via intrauterine or periconceptional mechanisms. We aimed to establish whether associations between parental peri-pregnancy body mass index (BMI) and offspring birth weight (BW), BMI until 8 years and 8-year eating behaviour are due to genetic confounding.MethodsWe used data from the Norwegian Mother, Father and Child Cohort Study and the Medical Birth Registry of Norway. We compared the strength of the associations of maternal versus paternal BMI with offspring outcomes, and used an extended children of twins structural equation model (SEM) to quantify the extent to which associations were due to genetic confounding (n = 17001 to 85866 children).FindingsMaternal BMI was more strongly associated than paternal BMI with offspring BW, but the maternal-paternal difference decreased for offspring BMI after birth. Greater parental BMI was associated with obesity-related offspring eating behaviours. SEM results indicated that genetic confounding did not explain the association between parental BMI and offspring BW, but explained the majority of the association with offspring BMI from 6 months onwards. For 8-year BMI, genetic confounding explained 79% (95% CI: 62%, 95%) of the covariance with maternal BMI and 94% (95% CI: 72%, 113%) of the covariance with paternal BMI.InterpretationWe found strong evidence that parent-child BMI associations are primarily due to genetic confounding, arguing against a strong causal effect of maternal or paternal adiposity on childhood adiposity via intrauterine or periconceptional mechanisms.

Background A joint, hierarchical structure of psychopathology and personality has been reported in adults but should also be investigated at earlier ages, as psychopathology often develops before adulthood. Here, we investigate the joint factor structure of psychopathology and personality in eight-year-old children, estimate factor heritability and explore external validity through associations with established developmental risk factors. Methods Phenotypic and biometric exploratory factor analyses with bifactor rotation on genetically informative data from the Norwegian Mother, Father, and Child Cohort (MoBa) study. The analytic sub-sample comprised 10 739 children (49% girls). Mothers reported their children's symptoms of depression (Short Moods and Feelings Questionnaire), anxiety (Screen for Anxiety Related Disorders), attention-deficit/hyperactivity disorder inattention and hyperactivity, oppositional-defiant disorder, conduct disorder (Parent/Teacher Rating Scale for Disruptive Behavior Disorders), and Big Five personality (short Hierarchical Personality Inventory for Children). Developmental risk factors (early gestational age and being small for gestational age) were collected from the Medical Birth Registry. Results Goodness-of-fit indices favored a p factor model with three residual latent factors interpreted as negative affectivity, positive affectivity, and antagonism, whereas psychometric indices favored a one-factor model. ADE solutions fitted best, and regression analyses indicated a negative association between gestational age and the p factor, for both the one- and four-factor solutions. Conclusion Correlations between normative and pathological traits in middle childhood mostly reflect one heritable and psychometrically interpretable p factor, although optimal fit to data required less interpretable residual latent factors. The association between the p factor and low gestational age warrants further study of early developmental mechanisms.

Purpose: On average, boys have lower academic achievement than girls. We investigated whether the timing of puberty is associated with academic achievement, and whether later puberty among boys contributes to the sex difference in academic achievement. Method: Examination scores at age 16 were studied among 13,477 British twins participating in the population-based Twins Early Development Study. A pubertal development scale, a height based proxy of growth spurt, and age at menarche were used as indicators of puberty. Associations between puberty, sex, and academic achievement were estimated in phenotypic mediation models and biometric twin models. Results: Earlier puberty was associated with higher academic achievement both in boys and girls. The exception was early age at menarche in girls, which associated with lower academic achievement. More than half of the sex differences in academic achievement could be linked to sex differences in pubertal development, but part of this association appeared to be rooted in prepubertal differences. The biometric twin modelling indicated that the association between puberty and academic achievement was due to shared genetic risk factors. Genetic influences on pubertal development accounted for 7%-8% of the phenotypic variation in academic achievement. Conclusions: Pubertal maturation relates to the examination scores of boys and of girls. This can give genes related to pubertal maturation an influence on outcomes in education and beyond. Sex differences in pubertal maturation can explain parts of the sex difference in academic achievement. Grading students when they are immature may not accurately measure their academic potential. (c) 2021 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Background Parental criticism is correlated with internalising symptoms in adolescent offspring. This correlation could in part reflect their genetic relatedness, if the same genes influence behaviours in both parents and offspring. We use a Children-of-Twins design to assess whether parent-reported criticism and offspring internalising symptoms remain associated after controlling for shared genes. To aid interpretation of our results and those of previous Children-of-Twins studies, we examine statistical power for the detection of genetic effects and explore the direction of possible causal effects between generations. Methods Data were drawn from two Swedish twin samples, comprising 876 adult twin pairs with adolescent offspring and 1,030 adolescent twin pairs with parents. Parent reports of criticism towards their offspring were collected concurrently with parent and offspring reports of adolescent internalising symptoms. Children-of-Twins structural equation models were used to control for genetic influence on the intergenerational association between parental criticism and adolescent internalising. Results Parental criticism was associated with adolescent internalising symptoms after controlling for genetic influence. No significant role was found for shared genes influencing phenotypes in both generations, although power analyses suggested that some genetic effects may have gone undetected. Models could not distinguish directionality for nongenetic, causal effects between generations. Conclusions Parental criticism may be involved in psychosocial family processes in the context of adolescent internalising. Future studies should seek to identify these processes and provide clarity on the direction of potential causal effects.

Indirect genetic effects from relatives may result in misleading quantifications of heritability, but can also be of interest in their own right. In this paper we propose Trio-GCTA, a model for separating direct and indirect genetic effects when genome-wide single nucleotide polymorphism data have been collected from parent-offspring trios. The model is applicable to phenotypes obtained from any of the family members. We discuss appropriate parameter interpretations and apply the method to three exemplar phenotypes: offspring birth weight, maternal relationship satisfaction, and paternal body-mass index, using real data from the Norwegian Mother, Father and Child Cohort Study (MoBa).

Objective Parent anxiety is associated with offspring internalizing problems (emotional problems related to anxiety and depression). This may reflect causal processes, whereby exposure to parent anxiety directly influences offspring internalizing (and/or vice versa). However, parent-offspring associations could also be attributable to their genetic relatedness. We present a systematic review and meta-analysis to investigate whether exposure to parent anxiety is associated with offspring internalizing after controlling for genetic relatedness. Method A literature search in five databases identified 429 records. Publications were retained if they used a quasi-experimental design in a general population sample to control for participant relatedness in associations between parent anxiety and offspring internalizing outcomes. Publications were excluded if they involved an experimental exposure or intervention. Studies of pre- and post-natal anxiety exposure were meta-analysed separately. Pearson’s correlation coefficient estimates (r) were pooled using multilevel random effects models. Results Eight publications were retained. Data were drawn from four population cohorts, each unique to a quasi-experimental design: adoption, sibling-comparison, children-of-twins or in-vitro-fertilisation. Cohorts were located in northern Europe or America. Families were predominantly of European ancestry. Three publications (Nfamilies>11,700; offspring aged 0.5—10 years) showed no association between prenatal anxiety exposure and offspring internalizing outcomes after accounting for participant relatedness (r=.04, CI -.07,.14). Six publications (Nfamilies>12,700; offspring aged 0.75—22 years) showed a small but significant association between concurrent symptoms in parents and offspring, after accounting for participant relatedness (r=.13, CI .04,.21). Conclusion Initial literature, derived from homogenous populations, suggests that prenatal anxiety exposure does not cause offspring internalizing outcomes. However, postnatal anxiety exposure may be causally associated with concurrent offspring internalizing, via non-genetic pathways. Longitudinal stability, child-to-parent effects, and the role of moderators and methodological biases require attention.

BackgroundAlthough selective serotonin reuptake inhibitors (SSRIs) are recommended for postnatal depression (PND) treatment, a lack of evidence regarding the long-term consequences of postnatal SSRI use have resulted in treatment hesitancy.MethodsThe current study used longitudinal data on a total of 60654 mother-child dyads enrolled in the Norwegian Mother and Child Cohort Study (MoBa) to examine associations between PND and maternal outcomes (depression and anxiety, relationship satisfaction) and child outcomes (motor and language development, emotional and behavioral problems) from birth to postpartum year 5. We tested whether postnatal SSRI treatment moderated the effects of PND on maternal and child outcomes. A propensity score was used to control for pre- /antenatal factors that impacted the probability of receiving SSRIs.ResultsPND was associated with poor maternal mental health outcomes and problems in child development. Use of SSRIs mitigated the associations between PND and later maternal mental health distress and child externalizing behaviors up to postpartum year 5. We found no evidence to indicate that the use of SSRIs was associated with increased risk of negative outcomes in emotional, behavioural, motor and language development in offspring.ConclusionsOur findings suggest that SSRI treatment for PND may bring benefits in the long term by attenuating the detrimental associations between PND and subsequent maternal depression and child externalizing behaviors. The study provides valuable information for clinicians and women with PND to help make informed decisions regarding treatment.

Polygenic scores now explain approximately 10% of the variation in educational attainment. However, they capture not only genetic propensity but also information about the family environment. This is because of passive gene–environment correlation, whereby the correlation between offspring and parent genotypes results in an association between offspring genotypes and the rearing environment. We measured passive gene–environment correlation using information on 6,311 adoptees in the UK Biobank. Adoptees’ genotypes were less correlated with their rearing environments because they did not share genes with their adoptive parents. We found that polygenic scores were twice as predictive of years of education in nonadopted individuals compared with adoptees ( R2s = .074 vs. .037, p = 8.23 × 10−24). Individuals in the lowest decile of polygenic scores for education attained significantly more education if they were adopted, possibly because of educationally supportive adoptive environments. Overall, these results suggest that genetic influences on education are mediated via the home environment.

Background: Theoretical models of the development of childhood externalizing disorders emphasize the role of parents. Empirical studies have not been able to identify specific aspects of parental behaviors explaining a considerable proportion of the observed individual differences in externalizing problems. The problem is complicated by the contribution of genetic factors to externalizing problems, as parents provide both genes and environments to their children. We studied the joint contributions of direct genetic effects of children and the indirect genetic effects of parents through the environment on externalizing problems. Methods: The study used genome-wide single nucleotide polymorphism data from 9,675 parent–offspring trios participating in the Norwegian Mother Father and child cohort study. Based on genomic relatedness matrices, we estimated the contribution of direct genetic effects and indirect maternal and paternal genetic effects on ADHD, conduct and disruptive behaviors at 8 years of age. Results: Models including indirect parental genetic effects were preferred for the ADHD symptoms of inattention and hyperactivity, and conduct problems, but not oppositional defiant behaviors. Direct genetic effects accounted for 11% to 24% of the variance, whereas indirect parental genetic effects accounted for 0% to 16% in ADHD symptoms and conduct problems. The correlation between direct and indirect genetic effects, or gene–environment correlations, decreased the variance with 16% and 13% for conduct and inattention problems, and increased the variance with 6% for hyperactivity problems. Conclusions: This study provides empirical support to the notion that parents have a significant role in the development of childhood externalizing behaviors. The parental contribution to decrease in variation of inattention and conduct problems by gene–environment correlations would limit the number of children reaching clinical ranges in symptoms. Not accounting for indirect parental genetic effects can lead to both positive and negative bias when identifying genetic variants for childhood externalizing behaviors. publishedVersion

Children with attention deficit hyperactivity disorder (ADHD) often experience co-occurring emotional problems. ADHD with this comorbidity is associated with poorer outcomes than ADHD without comorbidity. Better understanding of the etiology of comorbidity could improve prevention of negative outcomes for children with ADHD. The sample consisted of 567 twin pairs, 3,632 sibling pairs, and 2,340 cousin pairs from the Norwegian Mother, Father and Child Cohort Study. Mothers rated offspring symptoms of ADHD, anxiety, and depression at 8 years of age. Biometric modeling was performed to examine genetic and environmental contributions to co-occurring symptoms of ADHD and emotional problems in the children. We fitted four variable (inattention, hyperactivity/impulsivity, anxiety, and depression) covariance matrices of additive genetic, common environmental, twin- and individual-specific environmental effects. Genetic, shared environmental, and individual-specific environmental factors contributed to the correlation between ADHD and depression. The pattern was similar for both inattention and hyperactivity/impulsivity. Familial risk factors (genetic and shared environment), but not individual-specific environmental factors contributed to the positive correlations between each of the two ADHD subdomains and anxiety. The genetic contributions to ADHD-depression comorbidity only partly overlapped with genetic contributions to ADHD-anxiety comorbidity. Our findings indicate that shared risk factors for ADHD and comorbid depression were familial as well as individual-specific, while shared risk factors for ADHD and comorbid anxiety were primarily familial. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Background: Anxiety in parents is associated with anxiety in offspring, although little is known about the mechanisms underpinning these intergenerational associations. We conducted the first genetically sensitive study to simultaneously examine the effects of mother, father and child anxiety symptoms on each other over time. Method: Adoptive parent and child symptoms were measured at child ages 6, 7 and 8 years from 305 families involved in the Early Growth and Development Study, using a prospective adoption design. Children were adopted at birth to nonrelatives, and composite data on internalising problems within birth families were used as a proxy measure of offspring inherited risk for anxiety. Structural equation models were fitted to the data to examine prospective associations between adoptive mother, father and child symptoms, whilst accounting for individuals’ symptom stability over time. Results: Child anxiety symptoms at age 7 predicted adoptive mothers’ anxiety symptoms at age 8. No mother-to-child or child-to-father effects were observed. These results were consistent in sensitivity analyses using only paternal offspring reports and using a second measure of child anxiety symptoms. Fathers’ anxiety symptoms at child age 6 prospectively predicted child symptoms, but only when paternal offspring reports were included in the model. Composite data on birth family internalising problems were not associated with child anxiety symptoms. Conclusions: Results show environmentally mediated associations between parent and child anxiety symptoms. Results support developmental theories suggesting that child anxiety symptoms can exert influence on caregivers, and mothers and fathers may play unique roles during the development of child symptoms. Further research is needed on the role of genetic transmission associated with anxiety symptoms in biologically related families. In the meantime, researchers and clinicians should strive to include fathers in assessments and consider the effects of child symptoms on caregivers.

Background Children of parents with high levels of neuroticism tend to have high neuroticism themselves as well as increased risk of experiencing symptoms of anxiety and depression. It is not yet clear how much of this link is attributable to a potential effect of parent on child (e.g., via a socializing effect) versus to shared genetic risk. We aimed to determine whether there is an intergenerational association after accounting for genetic transmission and assortative mating. Methods We used data from the Norwegian Mother, Father and Child Cohort Study including 11,088 sibling pairs in the parental generation, their partners (N = 22,176) and their offspring (N = 26,091). Exposures were maternal and paternal neuroticism (self‐reported), and the outcomes were neuroticism, symptoms of depression, and symptoms of anxiety in 8‐year‐old children (mother‐reported). Results After accounting for assortative mating in parents (phenotypic r = 0.26) and genetic transmission (explaining 0%–18% of the mother‐offspring correlations), potential maternal effects explained 80% (95% CI = 47–95) of the association with offspring neuroticism (mother‐child r = 0.31), 78% (95% CI = 66–89) of the association with offspring depressive symptoms (r = 0.31), and 98% (95% CI = 45–112) of the association with offspring anxiety symptoms (r = 0.16). Intergenerational transmission of genetic variants associated with paternal neuroticism accounted for ∼40% (CI = 22%–58%) of the father‐offspring correlations with neuroticism and symptoms of depression (r = 0.13 and 0.13, respectively) but none with offspring symptoms of anxiety (r = 0.05). The remaining father‐offspring correlations were explained by maternal influences through assortative mating. Conclusions These results are consistent with direct effects between maternal and offspring neuroticism and between maternal neuroticism and offspring symptoms of anxiety and depression. Further understanding of these intergenerational processes will require an adequate model of how these constructs (neuroticism, anxiety and depression) relate to each other within generations.

Background: Low educational attainment in parents is associated with child psychopathology. It is not clear whether the associations are due to risk factors that family members share or due to effects of maternal or paternal education on the offspring. We investigate whether associations between maternal and paternal educational attainment and child symptoms of attention deficit/hyperactivity disorder (ADHD), depression, and academic problems are due to shared genetic factors, shared family environmental factors, or effects of the parental phenotype educational attainment itself. Methods: This study is based on the Norwegian Mother, Father and Child Cohort Study (MoBa). The sample comprised 34,958 children (17,128 girls) in 28,372 extended‐family units. We used data from related nuclear families linked by siblings in the parent generation. We applied a quasi‐experimental extended children‐of‐twins design that included siblings in both generations and took account of nonrandom mating by including partners. Educational attainment was self‐reported by mothers and fathers. Mothers reported children's symptoms of ADHD, symptoms of depression, and academic problems by questionnaire when the children were 8 years old. Results: Children of lowly educated parents scored higher on all outcomes and had an approximate doubling of the risk of high symptom levels. The association between maternal and paternal educational attainment and child symptoms of ADHD and academic problems persisted after controlling for shared genetic and family environmental factors. Phenotypic transmission to depression was weaker and in the best fitting model fully explained by genetic factors shared by the two generations. Conclusions: Associations between educational attainment of mothers and fathers and child symptoms of ADHD and academic problems could not be ascribed to shared familial risk factors, whereas associations with symptoms of depression could. Parental education or resources and behaviors resulting from low education might be targets of interventions aimed at reducing symptoms of ADHD and academic problems. publishedVersion

Indirect genetic effects from relatives may result in misleading quantifications of heritability, but can also be of interest in their own right. In this paper we propose Trio-GCTA, a model for separating direct and indirect genetic effects when genome-wide single nucleotide polymorphism data have been collected from parent-offspring trios. The model is applicable to phenotypes obtained from any of the family members. We discuss appropriate parameter interpretations and apply the method to three exemplar phenotypes: offspring birth weight, maternal relationship satisfaction, and paternal body-mass index, using real data from the Norwegian Mother, Father and Child Cohort Study (MoBa).

Indirect genetic effects from relatives may result in misleading quantifications of heritability, but can also be of interest in their own right. In this paper we propose Trio-GCTA, a model for separating direct and indirect genetic effects when genome-wide single nucleotide polymorphism data have been collected from parent-offspring trios. The model is applicable to phenotypes obtained from any of the family members. We discuss appropriate parameter interpretations and apply the method to four exemplar phenotypes; offspring birth weight, offspring temperament, maternal relationship satisfaction, and paternal body-mass index, using real data from the Norwegian Mother, Father and Child Cohort Study (MoBa).

BackgroundParental criticism is correlated with internalising symptoms in adolescent offspring. This correlation could in part reflect their genetic relatedness, if the same genes influence behaviours in both parents and offspring. We use a Children-of-Twins design to assess whether parent-reported criticism and offspring internalising symptoms remain associated after controlling for shared genes. To aid interpretation of our results and those of previous Children-of-Twins studies, we examine statistical power for the detection of genetic effects and explore the direction of possible causal effects between generations.MethodsData were drawn from two Swedish twin samples, comprising 876 adult twin pairs with adolescent offspring and 1030 adolescent twin pairs with parents. Parent reports of criticism towards their offspring were collected concurrently with parent and offspring reports of adolescent internalising symptoms. Children-of-Twins structural equation models were used to control for genetic influence on the intergenerational association between parental criticism and adolescent internalising.ResultsParental criticism was associated with adolescent internalising symptoms after controlling for genetic influence. No significant role was found for shared genes influencing phenotypes in both generations, although power analyses suggested that some genetic effects may have gone undetected. Models could not distinguish directionality for non-genetic, causal effects between generations.ConclusionsParental criticism may be involved in psychosocial family processes in the context of adolescent internalising. Future studies should seek to identify these processes and provide clarity on the direction of potential causal effects.

Objective: The primary aim of the present study was to separate the direct effect of maternal prenatal depression on offspring ADHD from the passive transmission of genetic liability. Method: A children-of-twins and siblings design including 17,070 extended-family units participating in the Norwegian Mother and Child Cohort Study was used. Self-ratings were obtained from parents using the Symptom Checklist during pregnancy. Maternal ratings using Conner’s Parent Rating Scale were obtained when the children were 5 years of age. Results: Genetic influences were important for explaining similarity between parents and offspring. There was also evidence for a maternal effect after accounting for genetic transmission ( m = 0.06, 95% confidence interval [CI] = [0.02, 0.09]). Conclusion: Our results were consistent with hypotheses suggesting that maternal prenatal depression influences symptoms of ADHD in offspring. However, the effect was weak and a substantial portion of the association could be accounted for by shared genetic influences.

We introduce the Parent Play Questionnaire (PPQ), a parent-report measure designed to assess frequency of parent-infant play, parents’ attitudes towards play with their infant, and infants’ use of digital media. We describe measure development and empirical data across three samples of parent-infant dyads (total N = 414, offspring aged 0.3 – 2.5 years). Three latent factors explain the PPQ, corresponding with theoretically defined subscales. Summary scores showed good internal consistency and normally distributed results. Weak to moderate correlations were found between the frequency and attitude play scales, and with standardised measures of family social and emotional characteristics. Overall, frequency of digital media use was not correlated with play or broader family variables. Results suggest that the PPQ will be a useful tool for researchers interested in assessing parent-child play during early childhood.

Background: Children of parents with high levels of neuroticism tend to have high neuroticism themselves, as well as increased risk of experiencing symptoms of anxiety and depression. It is not yet clear how much of this link is attributable to a potential effect of parent on child (e.g., via a socializing effect) vs. to shared genetic risk. Methods: This study is based on data from the Norwegian Mother, Father and Child Cohort Study. We used data from 11,088 sibling pairs in the parental generation, their partners (N= 22,176), and their offspring (N=26,091). Exposures were maternal and paternal neuroticism (self-reported), and the outcomes were neuroticism, symptoms of depression, and symptoms of anxiety in 8-year-old children (mother-reported). Outcomes: After accounting for assortative mating in parents (phenotypic r=0.26), genetic transmission of maternal neuroticism accounted for 16% of the correlation with offspring neuroticism (mother-child r=0.31), 18% of the association with offspring depressive symptoms (r=0.31), and 0% of the association with offspring anxiety symptoms (r=0.16). Intergenerational transmission of genes associated with paternal neuroticism accounted for ~40% of the father-offspring correlations with neuroticism and symptoms of depression (r=0.13 and 0.13, respectively) but none with offspring symptoms of anxiety (r=0.05). The remaining father-offspring correlations was explained by maternal influences through assortative mating. Interpretations: These results are consistent with direct effects between maternal and offspring neuroticism and between maternal neuroticism and offspring symptoms of anxiety and depression, suggesting that interventions targeted at family functioning could benefit the children. Funding Statement: This work was supported by the Research Council of Norway (RCN) (262177). E.M.E. and L.C.G. were funded by the RCN (262177). E.Y. was funded by the RCN (288083 and 262177). A.H. was supported by the South-Eastern Norway Regional Health Authority (2018059 and 2020022). T.A.McA. was supported by a Sir Henry Dale Fellowship, jointly funded by the Wellcome Trust and the Royal Society (107706/Z/15/Z) and the RCN (288083). L.J.H. was supported by funding from the SouthEastern Norway Regional Health Authority (2018058). F.A.T. was supported by the RCN (300668). This work was partly supported by the RCN through its Centres of Excellence funding scheme, project number 262700. Declaration of Interests: The authors have declared that they have no competing or potential conflicts of interest. Ethics Approval Statement: The establishment of MoBa and initial data collection was based on a license from the Norwegian Data protection agency and approval from The Regional Committees for Medical and Health Research Ethics. The MoBa cohort is based on regulations based on the Norwegian Health Registry Act. The current study was approved by The Regional Committees for Medical and Health Research Ethics.

Loos, Ruth J F/0000-0002-8532-5087; Huibregtse, Brooke M./0000-0003-0977-7249; Kandler, Christian/0000-0002-9175-235X; Hjelmborg, Jacob/0000-0001-9630-9149; mangino, massimo/0000-0002-2167-7470; Siribaddana, Sisira/0000-0001-5821-2557; Plomin, Robert/0000-0002-0756-3629; Latvala, Antti/0000-0001-5695-117X; Kaprio, Jaakko/0000-0002-3716-2455; Willemsen, Gonneke/0000-0003-3755-0236; Tan, Qihua/0000-0003-3194-0030; Pahlen, Shandell/0000-0003-0753-4155; Pedersen, Nancy/0000-0001-8057-3543; Haworth, Claire/0000-0002-8608-289X; Nistico, Lorenza/0000-0003-1805-6240; Skytthe, Axel/0000-0002-8629-4913; van Beijsterveldt, Toos/0000-0002-6617-4201; Rebato, Esther/0000-0003-1221-8501; Li, Lintao/0000-0002-0604-9660; Bartels, Meike/0000-0002-9667-7555; Silventoinen, Karri/0000-0003-1759-3079; Cunha Oliveira, Vinicius/0000-0002-8658-3774; Sund, Reijo/0000-0002-6268-8117; Sodemann, Morten/0000-0001-8992-2500; Rasmussen, Finn/0000-0001-7915-7809; Harden, Kathryn/0000-0002-1557-6737; Medda, Emanuela/0000-0003-4837-4549; Kyvik, Kirsten Ohm/0000-0003-2981-0245; Colodro Conde, Lucia/0000-0002-9004-364X WOS: 000517442200060 PubMed: 31364586 The COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) project is a large international collaborative effort to analyze individual-level phenotype data from twins in multiple cohorts from different environments. The main objective is to study factors that modify genetic and environmental variation of height, body mass index (BMI, kg/m(2)) and size at birth, and additionally to address other research questions such as long-term consequences of birth size. The project started in 2013 and is open to all twin projects in the world having height and weight measures on twins with information on zygosity. Thus far, 54 twin projects from 24 countries have provided individual-level data. The CODATwins database includes 489,981 twin individuals (228,635 complete twin pairs). Since many twin cohorts have collected longitudinal data, there is a total of 1,049,785 height and weight observations. For many cohorts, we also have information on birth weight and length, own smoking behavior and own or parental education. We found that the heritability estimates of height and BMI systematically changed from infancy to old age. Remarkably, only minor differences in the heritability estimates were found across cultural-geographic regions, measurement time and birth cohort for height and BMI. In addition to genetic epidemiological studies, we looked at associations of height and BMI with education, birth weight and smoking status. Within-family analyses examined differences within same-sex and opposite-sex dizygotic twins in birth size and later development. The CODATwins project demonstrates the feasibility and value of international collaboration to address gene-by-exposure interactions that require large sample sizes and address the effects of different exposures across time, geographical regions and socioeconomic status. Academy of FinlandAcademy of Finland [266592, 100499, 205585, 118555, 141054, 265240, 263278, 264146]; Osaka University's International Joint Research Promotion Program; Centre of Research Excellence Grant from the National Health and Medical Research CouncilNational Health and Medical Research Council of Australia [1079102]; National Institutes of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [R01 HD068435, R01 MH062375, 1R01ESO15150-01, R21 AG039572]; National Medical Research Council Research Fellowship; California Tobacco-Related Disease Research ProgramUniversity of California System [7RT-0134H, 8RT-0107H, 6RT-0354H]; National Institute on AgingUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Aging (NIA) [1RO1-AG13662-01A2]; Swedish Research Council through the Swedish Initiative for Research on Microdata in the Social And Medical Sciences (SIMSAM) [340-2013-5867]; Swedish Heart-Lung FoundationSwedish Heart-Lung Foundation; Swedish Asthma and Allergy Association's Research Foundation; Special Fund for Health Scientific Research in the Public Welfare, China [201502006]; NIDAUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Drug Abuse (NIDA) [DA011015, HD10333]; National Program for Research Infrastructure 2007 from the Danish Agency for Science, Technology and Innovation; Research Council for Health and Disease; Velux Foundation; US National Institute of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [P01 AG08761]; Fund of Scientific Research, FlandersFWO; ENGAGE - European Network for Genetic and Genomic Epidemiology, FP7-HEALTH-F4-2007 [201413]; National Institute of Alcohol Abuse and AlcoholismUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Alcohol Abuse & Alcoholism (NIAAA) [AA-12502, AA-00145, AA-09203]; Academy of Finland Center of Excellence in Complex Disease GeneticsAcademy of Finland [213506, 129680]; Cancer Research UKCancer Research UK [C1418/A7974]; W T Grant Foundation; University of London Central Research fund; Medical Research CouncilMedical Research Council UK (MRC) [G81/343, G120/635]; Economic and Social Research CouncilEconomic & Social Research Council (ESRC) [RES-000-22-2206]; Institute of Social Psychiatry [06/07-11]; Leverhulme Research FellowshipLeverhulme Trust [RF/2/RFG/2008/0145]; Goldsmiths, University of London; UK Medical Research CouncilMedical Research Council UK (MRC) [MR/M021475/1, G0901245]; National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London; NIHUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [R01AG053217, RC2 HL103416]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [81125007]; Global Research Network Program of the National Research Foundation [NRF 2011-220-E00006]; European Research Council (ERC)European Research Council (ERC) [240994]; Michigan State University; National Institute of Mental Health (NIMH)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Mental Health (NIMH) [R01-MH081813, R01-MH0820-54, R01-MH092377-02, R21-MH070542-01, R03-MH63851-01, 1R01-MH118848-01]; Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD) [R01-HD066040]; MSU Foundation [11-SPG-2518]; Fundacion Seneca, Regional Agency for Science and Technology, Murcia, Spain [08633/PHCS/08, 15302/PHCS/10, 19479/PI/14]; Ministry of Science and Innovation, SpainSpanish Government [PSI2009-11560, PSI2014-56680-R]; MagW/ZonMW [904-61-090, 985-10-002, 912-10-020, 904-61-193, 480-04-004, 463-06-001, 451-04-034, 400-05-717, Addiction-31160008, Middelgroot-911-09-032, Spinozapremie 56-464-14192]; European Research CouncilEuropean Research Council (ERC) [ERC-230374]; JSPS KAKENHI JP [23593419, 24792601, 26671010, 24590695, 26293128, 16K15385, 16K15978, 16K15989, 16H03261]; Australian National Health and Medical Research CouncilNational Health and Medical Research Council of Australia [437015, 607358]; Bonnie Babes Foundation [BBF20704]; Financial Markets Foundation for Children [032-2007]; Victorian Government; Portuguese agency for research (The Foundation for Science and Technology [FCT]) [POCI/DES/56834/2004]; Wellcome TrustWellcome Trust; Medical Research CouncilMedical Research Council UK (MRC); European UnionEuropean Union (EU); National Institute for Health Research (NIHR)National Institute for Health Research (NIHR); King's College London; Fonds Quebecois de la Recherche sur la Societe et la CultureFQRNT; Fonds de la Recherche en Sante du QuebecFonds de la Recherche en Sante du Quebec; Social Science and Humanities Research Council of Canada; National Health Research Development Program; Canadian Institutes for Health ResearchCanadian Institutes of Health Research (CIHR); Sainte-Justine Hospital's Research Center; Canada Research Chair ProgramCanada Research Chairs; National Research Foundation of KoreaNational Research Foundation of Korea [NRF-371-2011-1 B00047]; Swedish Research CouncilSwedish Research Council [2017-00641]; UK Biotechnology and Biological Sciences Research CouncilBiotechnology and Biological Sciences Research Council (BBSRC) [31/D19086]; MRCMedical Research Council UK (MRC) [MR/M021475/1]; Krkkale University [2009/43]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114C117]; National Institute of Mental HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Mental Health (NIMH) [R01 MH58354]; National Institute of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [NIA R01 AG018384, R01 AG018386, R01 AG022381, R01 AG022982]; VA San Diego Center of Excellence for Stress and Mental Health; Cooperative Studies Program of the Office of Research & Development of the United States Department of Veterans Affairs; Japan Society for the Promotion of ScienceMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science [15H05105]; Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust; Stockholm County Council (ALF-projects)Stockholm County Council; Twins, a nonprofit Association for Scientific Research in Multiple Births (Belgium); [5T32DA017637]; [5T32AG052371] This study was conducted within the CODATwins project (Academy of Finland #266592). K Silventoinen is supported by Osaka University's International Joint Research Promotion Program. This research was facilitated through access to Twins Research Australia, a national resource supported by a Centre of Research Excellence Grant (ID: 1079102), from the National Health and Medical Research Council. The Boston University Twin Project is funded by grants (#R01 HD068435 #R01 MH062375) from the National Institutes of Health to K. Saudino. Paulo Ferreira is funded by a National Medical Research Council Research Fellowship. California Twin Program was supported by The California Tobacco-Related Disease Research Program (7RT-0134H, 8RT-0107H, 6RT-0354H) and the National Institutes of Health (1R01ESO15150-01).; The Carolina African American Twin Study of Aging (CAATSA) was funded by a grant from the National Institute on Aging (grant 1RO1-AG13662-01A2) to K. E. Whitfield. The CATSS-Study is supported by the Swedish Research Council through the Swedish Initiative for Research on Microdata in the Social And Medical Sciences (SIMSAM) framework grant no 340-2013-5867, grants provided by the Stockholm County Council (ALF-projects), the Swedish Heart-Lung Foundation and the Swedish Asthma and Allergy Association's Research Foundation.; Chinese National Twin Registry is funded by Special Fund for Health Scientific Research in the Public Welfare (Project No: 201502006), China. Colorado Twin Registry is funded by NIDA-funded center grant DA011015, & Longitudinal Twin Study HD10333; Author Huibregtse is supported by 5T32DA017637 and 5T32AG052371. Danish Twin Registry is supported by the National Program for Research Infrastructure 2007 from the Danish Agency for Science, Technology and Innovation, The Research Council for Health and Disease, the Velux Foundation and the US National Institute of Health (P01 AG08761). Since its origin, the East Flanders Prospective Survey has been partly supported by grants from the Fund of Scientific Research, Flanders and Twins, a nonprofit Association for Scientific Research in Multiple Births (Belgium). Data collection and analyses in Finnish twin cohorts have been supported by ENGAGE - European Network for Genetic and Genomic Epidemiology, FP7-HEALTH-F4-2007, grant agreement number 201413, National Institute of Alcohol Abuse and Alcoholism (grants AA-12502, AA-00145 and AA-09203 to R J Rose, the Academy of Finland Center of Excellence in Complex Disease Genetics (grant numbers: 213506, 129680), and the Academy of Finland (grants 100499, 205585, 118555, 141054, 265240, 263278 and 264146 to J Kaprio). Gemini was supported by a grant from Cancer Research UK (C1418/A7974). Waves 1-3 of Genesis 12-19 were funded by the W T Grant Foundation, the University of London Central Research fund and a Medical Research Council Training Fellowship (G81/343) and Career Development Award (G120/635) to Thalia C. Eley. Wave 4 was supported by grants from the Economic and Social Research Council (RES-000-22-2206) and the Institute of Social Psychiatry (06/07-11) to Alice M. Gregory, who was also supported at that time by a Leverhulme Research Fellowship (RF/2/RFG/2008/0145). Wave 5 was supported by funding to Alice M. Gregory from Goldsmiths, University of London. T. C. Eley is partly funded by a program grant from the UK Medical Research Council (MR/M021475/1).; This study presents independent research [partly] funded by the National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. The Minnesota Twin Registry (MTR) acknowledges support from NIH grant R01AG053217. Guangzhou Twin Eye Study is supported by National Natural Science Foundation of China (grant #81125007). Anthropometric measurements of the Hungarian twins were supported by Medexpert Ltd., Budapest, Hungary. Korean Twin-Family Register was supported by the Global Research Network Program of the National Research Foundation (NRF 2011-220-E00006). Longitudinal Israeli Study of Twins was funded by the Starting Grant no. 240994 from the European Research Council (ERC) to Ariel Knafo. The Michigan State University Twin Registry has been supported by Michigan State University, as well as grants R01-MH081813, R01-MH0820-54, R01-MH092377-02, R21-MH070542-01, R03-MH63851-01 and 1R01-MH118848-01 from the National Institute of Mental Health (NIMH), R01-HD066040 from the Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD) and 11-SPG-2518 from the MSU Foundation. The content of this paper is solely the responsibility of the authors and does not necessarily represent the official views of the NIMH, the NICHD or the National Institutes of Health. The Murcia Twin Registry is supported by Fundacion Seneca, Regional Agency for Science and Technology, Murcia, Spain (08633/PHCS/08, 15302/PHCS/10 & 19479/PI/14) and Ministry of Science and Innovation, Spain (PSI2009-11560 & PSI2014-56680-R). The NAS-NRC Twin Registry acknowledges financial support from the National Institutes of Health grant number R21 AG039572. Netherlands Twin Register acknowledges the Netherlands Organization for Scientific Research (NWO) and MagW/ZonMW grants 904-61-090, 985-10-002, 912-10-020, 904-61-193,480-04-004, 463-06-001, 451-04-034, 400-05-717, Addiction-31160008, Middelgroot-911-09-032, Spinozapremie 56-464-14192; VU University's Institute for Health and Care Research (EMGO+); the European Research Council (ERC-230374), the Avera Institute, Sioux Falls, South Dakota (USA). Osaka University Aged Twin Registry is supported by grants from JSPS KAKENHI JP (23593419, 24792601, 26671010, 24590695, 26293128, 16K15385, 16K15978, 16K15989, 16H03261). PETS was supported by grants from the Australian National Health and Medical Research Council (grant numbers 437015 and 607358 to JC, and RS), the Bonnie Babes Foundation (grant number BBF20704 to JMC), the Financial Markets Foundation for Children (grant no. 032-2007 to JMC), and by the Victorian Government's Operational Infrastructure Support Program.; Madeira data comes from the following project: Genetic and environmental influences on physical activity, fitness and health: the Madeira family study Project reference: POCI/DES/56834/2004 Founded by the Portuguese agency for research (The Foundation for Science and Technology [FCT]). TwinsUK receives funding from the Wellcome Trust, Medical Research Council and European Union.; TwinsUK and M. Mangino are supported by the National Institute for Health Research (NIHR)-funded BioResource, Clinical Research Facility and Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust in partnership with King's College London. The Quebec Newborn Twin Study acknowledges financial support from the Fonds Quebecois de la Recherche sur la Societe et la Culture, the Fonds de la Recherche en Sante du Quebec, the Social Science and Humanities Research Council of Canada, the National Health Research Development Program, the Canadian Institutes for Health Research, Sainte-Justine Hospital's Research Center, and the Canada Research Chair Program (Michel Boivin). South Korea Twin Registry is supported by National Research Foundation of Korea (NRF-371-2011-1 B00047). We acknowledge The Swedish Twin Registry for access to data. The Swedish Twin Registry is managed by Karolinska Institutet and receives funding through the Swedish Research Council under the grant no. 2017-00641.; The Twins Early Development Study (TEDS) is supported by a program grant (G0901245) from the UK Medical Research Council and the work on obesity in TEDS is supported in part by a grant from the UK Biotechnology and Biological Sciences Research Council (31/D19086). Currently TEDS is supported by MRC grant 'MR/M021475/1'. The Texas Twin Project is currently funded by grant R01HD083613 from the National Institutes of Health. S. Y. oncel and F. Aliev are supported by Krkkale University Research Grant: KKU, 2009/43 and TUBITAK grant 114C117. The University of Southern California Twin Study is funded by a grant from the National Institute of Mental Health (R01 MH58354). Washington State Twin Registry (formerly the University of Washington Twin Registry) was supported in part by grant NIH RC2 HL103416 (D. Buchwald, PI). Vietnam Era Twin Study of Aging was supported by National Institute of Health grants NIA R01 AG018384, R01 AG018386, R01 AG022381 and R01 AG022982, and, in part, with resources of the VA San Diego Center of Excellence for Stress and Mental Health. The Cooperative Studies Program of the Office of Research & Development of the United States Department of Veterans Affairs has provided financial support for the development and maintenance of the Vietnam Era Twin (VET) Registry. The content of this paper is solely the responsibility of the authors and does not necessarily represent the official views of the NIA/NIH, or the VA. The West Japan Twins and Higher Order Multiple Births Registry was supported by Grant-in-Aid for Scientific Research (B) (grant number 15H05105) from the Japan Society for the Promotion of Science.

Individual-level polygenic scores can now explain ∼10% of the variation in number of years of completed education. However, associations between polygenic scores and education capture not only genetic propensity but information about the environment that individuals are exposed to. This is because individuals passively inherit effects of parental genotypes, since their parents typically also provide the rearing environment. In other words, the strong correlation between offspring and parent genotypes results in an association between the offspring genotypes and the rearing environment. This is termed passive gene-environment correlation. We present an approach to test for the extent of passive gene-environment correlation for education without requiring intergenerational data. Specifically, we use information from 6311 individuals in the UK Biobank who were adopted in childhood to compare genetic influence on education between adoptees and non-adopted individuals. Adoptees’ rearing environments are less correlated with their genotypes, because they do not share genes with their adoptive parents. We find that polygenic scores are twice as predictive of years of education in non-adopted individuals compared to adoptees (R2= 0.074 vs 0.037, difference test p= 8.23 × 10−24). We provide another kind of evidence for the influence of parental behaviour on offspring education: individuals in the lowest decile of education polygenic score attain significantly more education if they are adopted, possibly due to educationally supportive adoptive environments. Overall, these results suggest that genetic influences on education are mediated via the home environment. As such, polygenic prediction of educational attainment represents gene-environment correlations just as much as it represents direct genetic effects.

This study investigated associations between mindfulness and symptoms of insomnia, depression and anxiety. Mindfulness was disaggregated into five subscales: ‘nonreactivity to inner experience’, ‘observing’, ‘acting with awareness’, ‘describing’ and ‘nonjudging of inner experience’. Twin models were used to examine genetic and environmental influences on mindfulness, symptoms of insomnia, depression and anxiety and on their associations. Data came from a longitudinal twin/sibling study (G1219) comprising 862 individuals (age range 22–32 years, 66% females). Less mindfulness was associated with greater symptoms of insomnia, depression and anxiety (r = .22-.48). Of the mindfulness subscales, ‘nonjudging of inner experience’ was most strongly associated with the other traits. Overall mindfulness was largely influenced by non-shared environmental factors (E = .72) although familial influences played a role for overall mindfulness, as well as for the ‘acting with awareness’ and ‘describing’ subscales. The genetic correlations between overall mindfulness and symptoms of insomnia, depression and anxiety ranged from .32 to .75 (but were non-significant), while the shared environmental correlations ranged from −.78 to .79 (also non-significant). The non-shared environmental influences between these three variables were moderately, significantly correlated (rE = .21-.55).

The Children of the Twins Early Development Study (CoTEDS) is a new prospective children-of-twins study in the UK, designed to investigate intergenerational associations across child developmental stages. CoTEDS will enable research on genetic and environmental factors that underpin parent–child associations, with a focus on mental health and cognitive-related traits. Through CoTEDS, we will have a new lens to examine the roles that parents play in influencing child development, as well as the genetic and environmental factors that shape parenting behavior and experiences. Recruitment is ongoing from the sample of approximately 20,000 contactable adult twins who have been enrolled in the Twins Early Development Study (TEDS) since infancy. TEDS twins are invited to register all offspring to CoTEDS at birth, with 554 children registered as of May 2019. By recruiting the second generation of TEDS participants, CoTEDS will include information on adult twins and their offspring from infancy. Parent questionnaire-based data collection is now underway for 1- and 2-year-old CoTEDS infants, with further waves of data collection planned. Current data collection includes the following primary constructs: child mental health, temperament, language and cognitive development; parent mental health and social relationships; parenting behaviors and feelings; and other socioecological factors. Measurement tools have been selected with reference to existing genetically informative cohort studies to ensure overlap in phenotypes measured at corresponding stages of development. This built-in study overlap is intended to enable replication and triangulation of future analyses across samples and research designs. Here, we summarize study protocols and measurement procedures and describe future plans.

BackgroundAlthough maternal depressive symptoms are robustly associated with offspring early-life psychopathology symptoms, it is not clear which potential mechanisms are at play. We aimed to estimate the relative importance of genetic transmission and direct environmental exposure in these associations on three occasions in early childhood.MethodsBiometric modeling of maternal sisters and their offspring from the Norwegian Mother and Child Cohort Study. The analyzed sample comprised 22 316 mothers and 35 589 offspring. Mothers reported their own depressive symptoms using the Symptom checklist, and offspring's concurrent symptoms of psychopathology using the Child Behavior Checklist at 1.5, 3, and 5 years postpartum.ResultsAssociations between maternal symptoms of depression and offspring emotional problems were predominantly explained by passive genetic transmission at 1.5 and 3 years postpartum. At age 5, associations were more due to direct environmental exposure. For offspring behavioral problems, there was no net increase in the importance of direct environmental exposure across occasions.ConclusionsAssociations between maternal depressive symptoms and offspring psychopathology symptoms remained after accounting for shared genes, consistent with a small, causal effect. For offspring emotional problems, this effect appeared to increase in importance over time. Our findings imply that treatment of maternal depressive symptoms could also benefit the offspring, and that genetic confounding should be considered in future studies of such mother–offspring associations.

Do associations between maternal anxiety symptoms and offspring mental health remain after comparing differentially exposed siblings? Participants were 17,724 offspring siblings and 11,553 mothers from the Norwegian Mother and Child Cohort study. Mothers reported anxiety and depressive symptoms at 30 weeks' gestation, and 0.5, 1.5, 3, and 5 years postpartum. Child internalizing and externalizing problems were assessed at ages 1.5, 3, and 5, and modeled using multilevel analyses with repeated measures nested within siblings, nested within mothers. Maternal pre- and postnatal anxiety were no longer associated with child internalizing or externalizing problems after adjusting for maternal depression and familial confounding. Maternal anxiety when the children were in preschool age, however, remained significantly associated with child internalizing but not externalizing problems.

Kandler, Christian/0000-0002-9175-235X; Bartels, Meike/0000-0002-9667-7555; Medland, Sarah E/0000-0003-1382-380X; Kaprio, Jaakko/0000-0002-3716-2455; Fagnani, Corrado/0000-0001-5771-7772; de Freitas, Duarte Luis/0000-0001-6642-3370; Hjelmborg, Jacob/0000-0001-9630-9149; mangino, massimo/0000-0002-2167-7470; Busjahn, Andreas/0000-0001-9650-6919; Montgomery, Grant W/0000-0002-4140-8139; Moller, Soren/0000-0003-0858-4269; Heikkila, Kauko/0000-0002-9256-8028; Skytthe, Axel E/0000-0002-8629-4913; Christensen, Kaare/0000-0002-5429-5292; Knafo-Noam, Ariel/0000-0003-0613-1960; ONCEL, Sevgi YURT/0000-0002-0990-292X; Sund, Reijo/0000-0002-6268-8117; Aliev, Fazil/0000-0001-8357-4699; Magnusson, Patrik/0000-0002-7315-7899; Huibregtse, Brooke M./0000-0003-0977-7249; Loos, Ruth J F/0000-0002-8532-5087; Boivin, Michel/0000-0001-8621-9844; Kyvik, Kirsten Ohm/0000-0003-2981-0245; Pahlen, Shandell/0000-0003-0753-4155; van Beijsterveldt, Toos/0000-0002-6617-4201; McAdams, Tom/0000-0002-6825-3499; Sodemann, Morten/0000-0001-8992-2500; Pedersen, Nancy/0000-0001-8057-3543; Derom, Catherine/0000-0001-5574-796X; Plomin, Robert/0000-0002-0756-3629; Rebato, Esther/0000-0003-1221-8501; Saffery, Richard/0000-0002-9510-4181; Harden, Kathryn/0000-0002-1557-6737; Willemsen, Gonneke/0000-0003-3755-0236; Aaltonen, Sari/0000-0002-2873-4263; Silventoinen, Karri/0000-0003-1759-3079; Rasmussen, Finn/0000-0001-7915-7809; Haworth, Claire/0000-0002-8608-289X; Llewellyn, Clare/0000-0002-0066-2827 WOS: 000381870200017 PubMed: 27413137 Background: Both genetic and environmental factors are known to affect body mass index (BMI), but detailed understanding of how their effects differ during childhood and adolescence is lacking. Objectives: We analyzed the genetic and environmental contributions to BMI variation from infancy to early adulthood and the ways they differ by sex and geographic regions representing high (North America and Australia), moderate (Europe), and low levels (East Asia) of obesogenic environments. Design: Data were available for 87,782 complete twin pairs from 0.5 to 19.5 y of age from 45 cohorts. Analyses were based on 383,092 BMI measurements. Variation in BMI was decomposed into genetic and environmental components through genetic structural equation modeling. Results: The variance of BMI increased from 5 y of age along with increasing mean BMI. The proportion of BMI variation explained by additive genetic factors was lowest at 4 y of age in boys (a(2) = 0.42) and girls (a(2) = 0.41) and then generally increased to 0.75 in both sexes at 19 y of age. This was because of a stronger influence of environmental factors shared by co-twins in midchildhood. After 15 y of age, the effect of shared environment was not observed. The sex-specific expression of genetic factors was seen in infancy but was most prominent at 13 y of age and older. The variance of BMI was highest in North America and Australia and lowest in East Asia, but the relative proportion of genetic variation to total variation remained roughly similar across different regions. Conclusions: Environmental factors shared by co-twins affect BMI in childhood, but little evidence for their contribution was found in late adolescence. Our results suggest that genetic factors play a major role in the variation of BMI in adolescence among populations of different ethnicities exposed to different environmental factors related to obesity. CODATwins project (Academy of Finland) [266592]; NIHUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [R01 HD068435, R01 MH062375, 1R01ESO15150-01, HD081437, AA023322, RC2 HL103416]; California Tobacco-Related Disease Research ProgramUniversity of California System [7RT-0134H, 8RT-0107H, 6RT-0354H]; Special Fund for Health Scientific Research in the Public Welfare, China [201502006]; NIDAUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Drug Abuse (NIDA) [DA011015, HD10333]; National Program for Research Infrastructure from the Danish Agency for Science, Technology and Innovation, The Research Council for Health and Disease; Velux Foundation; US NIH grantUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [P01 AG08761]; Fund of Scientific Research, Flanders and Twins, a nonprofit Association for Scientific Research in Multiple Births (Belgium); ENGAGE-European Network for Genetic and Genomic Epidemiology, FP7-HEALTH-F4 [201413]; National Institute of Alcohol Abuse and AlcoholismUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Alcohol Abuse & Alcoholism (NIAAA) [AA-12502, AA-00145, AA-09203]; Academy of Finland Center of Excellence in Complex Disease Genetics grantAcademy of Finland [213506, 129680]; Academy of Finland grantAcademy of Finland [100499, 205585, 118555, 141054, 265240, 263278, 264146]; Osaka University's International Joint Research Promotion Program; Cancer Research UKCancer Research UK [C1418/A7974]; W T Grant Foundation; University of London Central Research fund; Medical Research CouncilMedical Research Council UK (MRC) [G81/343, G120/635]; Economic and Social Research CouncilEconomic & Social Research Council (ESRC) [RES-000-22-2206]; Institute of Social Psychiatry [06/07-11]; Leverhulme Research Fellowship grant [RF/2/RFG/2008/0145]; Goldsmiths, University of London, United Kingdom; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [81125007]; Medexpert Ltd., Budapest, Hungary; European Research CouncilEuropean Research Council (ERC) [240994, 230374]; Michigan State University; National Institute of Mental HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Mental Health (NIMH) [R01-MH081813, R01-MH0820-54, R01-MH092377-02, R21-MH070542-01, R03-MH63851-01]; Eunice Kennedy Shriver National Institute for Child Health and Human DevelopmentUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD) [R01-HD066040]; MSU Foundation [11-SPG-2518]; NIH grantUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [R21 AG039572]; MagW/ZonMW grant [904-61-090, 985-10-002, 912-10-020, 904-61-193, 480-04-004, 463-06-001, 451-04-034, 400-05-717, Addiction-31160008, Middelgroot-911-09-032, Spinozapremie 56-464- 14192]; VU University's Institute for Health and Care Research; Avera Institute, Sioux Falls, SD; Australian National Health and Medical Research Council grantNational Health and Medical Research Council of Australia [437015, 607358]; Bonnie Babes Foundation [BBF20704]; Financial Markets Foundation for Children grant [032-2007]; Victorian Government's Operational Infrastructure Support Program; Portuguese agency for research (The Foundation for Science and Technology) [POCI/DES/56834/2004]; Fonds Quebecois de la Recherche sur la Societe et la CultureFQRNT; Fonds de la Recherche en Sante du QuebecFonds de la Recherche en Sante du Quebec; Social Science and Humanities Research Council of Canada; National Health Research Development Program; Canadian Institutes for Health ResearchCanadian Institutes of Health Research (CIHR); Sainte-Justine Hospital's Research Center; Canada Research Chair ProgramCanada Research Chairs; National Research Foundation of KoreaNational Research Foundation of Korea [NRF-371-2011-1 B00047]; UK Medical Research CouncilMedical Research Council UK (MRC) [G0901245]; UK Biotechnology and Biological Sciences Research Council grant [31/D19086]; Kirikkale University Research grantKirikkale University [KKU 2009/43]; TUBITAK grantTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114C117]; European CommunityEuropean Community (EC); National Institute for Health Research BioResource Clinical Research Facility and Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London, United Kingdom; National Institute of Mental Health grantUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Mental Health (NIMH) [R01 MH58354]; Japan Society for the Promotion of ScienceMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science [15H05105]; [5T32DA017637-11]; Medical Research CouncilMedical Research Council UK (MRC) [G0901245]; NNF Center for Basic Metabolic ResearchNovo Nordisk Foundation [Metabolic Genetics]; Novo Nordisk FondenNovo NordiskNovo Nordisk Foundation [NNF10CC1016515] This study was conducted within the CODATwins project (Academy of Finland #266592). Support for participating twin projects: The Boston University Twin Project is funded by grants R01 HD068435 and R01 MH062375 from the NIH to KS. California Twin Program was supported by The California Tobacco-Related Disease Research Program grants 7RT-0134H, 8RT-0107H, and 6RT-0354H and by NIH grant 1R01ESO15150-01. Chinese National Twin Registry is funded by Special Fund for Health Scientific Research in the Public Welfare (Project No: 201502006), China. Colorado Twin Registry is funded by NIDA funded center grant DA011015, and Longitudinal Twin Study HD10333; BMH is supported by to 5T32DA017637-11. Danish Twin Registry is supported by the National Program for Research Infrastructure 2007 from the Danish Agency for Science, Technology and Innovation, The Research Council for Health and Disease, the Velux Foundation and the US NIH grant P01 AG08761. Since its origin the East Flanders Prospective Survey has been partly supported by grants from the Fund of Scientific Research, Flanders and Twins, a nonprofit Association for Scientific Research in Multiple Births (Belgium). Data collection and analyses in Finnish twin cohorts have been supported by ENGAGE-European Network for Genetic and Genomic Epidemiology, FP7-HEALTH-F4-2007, grant agreement 201413; National Institute of Alcohol Abuse and Alcoholism grants AA-12502, AA-00145, and AA-09203 to RJR; the Academy of Finland Center of Excellence in Complex Disease Genetics grants 213506 and 129680; and the Academy of Finland grants 100499, 205585, 118555, 141054, 265240, 263278, and 264146 to JK. KS is supported by Osaka University's International Joint Research Promotion Program. Gemini was supported by a grant from Cancer Research UK (C1418/A7974). Waves 1-3 of Genesis 12-19 were funded by the W T Grant Foundation, the University of London Central Research fund and Medical Research Council Training Fellowship grant G81/343 and Career Development Award G120/635 to TCE. Wave 4 was supported by the Economic and Social Research Council grant RES-000-22-2206 and the Institute of Social Psychiatry (06/07-11) to AMG, who was also supported at that time by a Leverhulme Research Fellowship grant RF/2/RFG/2008/0145. Wave 5 was supported by funding to AMG from Goldsmiths, University of London, United Kingdom. Guangzhou Twin Eye Study is supported by National Natural Science Foundation of China grant 81125007. Anthropometric measurements of the Hungarian twins were supported by Medexpert Ltd., Budapest, Hungary. Longitudinal Israeli Study of Twins was funded by the Starting Grant 240994 from the European Research Council to AK. The Michigan State University Twin Registry has been supported by Michigan State University, as well as grants R01-MH081813, R01-MH0820-54, R01-MH092377-02, R21-MH070542-01, and R03-MH63851-01 from the National Institute of Mental Health, R01-HD066040 from the Eunice Kennedy Shriver National Institute for Child Health and Human Development, and 11-SPG-2518 from the MSU Foundation. The NAS-NRC Twin Registry acknowledges financial support from NIH grant R21 AG039572. Netherlands Twin Register acknowledges the Netherlands Organization for Scientific Research and MagW/ZonMW grants 904-61-090, 985-10-002, 912-10-020, 904-61-193,480-04-004, 463-06-001, 451-04-034, and 400-05-717, Addiction-31160008, Middelgroot-911-09-032, Spinozapremie 56-464- 14192; VU University's Institute for Health and Care Research; the European Research Council grant 230374; and the Avera Institute, Sioux Falls, SD.; PETS was supported by the Australian National Health and Medical Research Council grant 437015 and 607358 to JC and RS, the Bonnie Babes Foundation grant BBF20704 to JMC, the Financial Markets Foundation for Children grant 032-2007 to JMC, and by the Victorian Government's Operational Infrastructure Support Program. Madeira data comes from the following project: Genetic and environmental influences on physical activity, fitness and health: the Madeira family study Project reference: POCI/DES/56834/2004 Founded by the Portuguese agency for research (The Foundation for Science and Technology). The Quebec Newborn Twin Study acknowledges financial support from the Fonds Quebecois de la Recherche sur la Societe et la Culture, the Fonds de la Recherche en Sante du Quebec, the Social Science and Humanities Research Council of Canada, the National Health Research Development Program, the Canadian Institutes for Health Research, Sainte-Justine Hospital's Research Center, and the Canada Research Chair Program (MB). South Korea Twin Registry is supported by National Research Foundation of Korea grant NRF-371-2011-1 B00047. The Texas Twin Project is currently funded by grants AA023322 and HD081437 from the NIH. The Twins Early Development Study is supported by program grant G0901245 from the UK Medical Research Council and the work on obesity in the Twins Early Development Study is supported in part by the UK Biotechnology and Biological Sciences Research Council grant 31/D19086. SYO and FA are supported by Kirikkale University Research grant KKU 2009/43 and TUBITAK grant 114C117. TwinsUK was funded by European Community's Seventh Framework Programme grant FP7/2007-2013. The study also receives support from the National Institute for Health Research BioResource Clinical Research Facility and Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London, United Kingdom. The University of Southern California Twin Study is funded by the National Institute of Mental Health grant R01 MH58354. University of Washington Twin Registry was supported in part by grant NIH RC2 HL103416 (D and PI). The West Japan Twins and Higher Order Multiple Births Registry was supported by Grant-in-Aid for Scientific Research (B) grant 15H05105 from the Japan Society for the Promotion of Science.

In this review, we discuss how samples comprising monozygotic and dizygotic twin pairs can be used for the purpose of strengthening causal inference by controlling for shared influences on exposure and outcome. We begin by briefly introducing how twin data can be used to inform the biometric decomposition of population variance into genetic, shared environmental, and nonshared environmental influences. We then discuss how extensions to this model can be used to explore whether associations between exposure and outcome survive correction for shared etiology (common causes). We review several analytical approaches that can be applied to twin data for this purpose. These include multivariate structural equation models, cotwin control methods, direction of causation models (cross-sectional and longitudinal), and extended family designs used to assess intergenerational associations. We conclude by highlighting some of the limitations and considerations that researchers should be aware of when using twin data for the purposes of interrogating causal hypotheses.

The parental feeding practices (PFPs) of excessive restriction of food intake (‘restriction’) and pressure to increase food consumption (‘pressure’) have been argued to causally influence child weight in opposite directions (high restriction causing overweight; high pressure causing underweight). However child weight could also ‘elicit’ PFPs. A novel approach is to investigate gene-environment correlation between child genetic influences on BMI and PFPs. Genome-wide polygenic scores (GPS) combining BMI-associated variants were created for 10,346 children (including 3,320 DZ twin pairs) from the Twins Early Development Study using results from an independent genome-wide association study meta-analysis. Parental ‘restriction’ and ‘pressure’ were assessed using the Child Feeding Questionnaire. Child BMI standard deviation scores (BMI-SDS) were calculated from children’s height and weight at age 10. Linear regression and fixed family effect models were used to test between- (n = 4,445 individuals) and within-family (n = 2,164 DZ pairs) associations between the GPS and PFPs. In addition, we performed multivariate twin analyses (n = 4,375 twin pairs) to estimate the heritabilities of PFPs and the genetic correlations between BMI-SDS and PFPs. The GPS was correlated with BMI-SDS (β = 0.20, p = 2.41x10-38). Consistent with the gene-environment correlation hypothesis, child BMI GPS was positively associated with ‘restriction’ (β = 0.05, p = 4.19x10-4), and negatively associated with ‘pressure’ (β = -0.08, p = 2.70x10-7). These results remained consistent after controlling for parental BMI, and after controlling for overall family contributions (within-family analyses). Heritabilities for ‘restriction’ (43% [40–47%]) and ‘pressure’ (54% [50–59%]) were moderate-to-high. Twin-based genetic correlations were moderate and positive between BMI-SDS and ‘restriction’ (rA = 0.28 [0.23–0.32]), and substantial and negative between BMI-SDS and ‘pressure’ (rA = -0.48 [-0.52 - -0.44]. Results suggest that the degree to which parents limit or encourage children’s food intake is partly influenced by children’s genetic predispositions to higher or lower BMI. These findings point to an evocative gene-environment correlation in which heritable characteristics in the child elicit parental feeding behaviour., Author summary It is widely believed that parents influence their child’s BMI via certain feeding practices. For example, rigid restriction has been argued to cause overweight, and pressuring to eat to cause underweight. However, recent longitudinal research has not supported this model. An alternative hypothesis is that child BMI, which has a strong genetic basis, evokes parental feeding practices (‘gene-environment correlation’). To test this, we applied two genetic methods in a large sample of 10-year-old children from the Twins Early Development Study: a polygenic score analysis (DNA-based score of common genetic variants associated with BMI in genome-wide meta-analyses), and a twin analysis (comparing resemblance between identical and non-identical twin pairs). Polygenic scores correlated positively with parental restriction of food intake (‘restriction’; β = 0.05, p = 4.19x10-4), and negatively with parental pressure to increase food intake (‘pressure’; β = -0.08, p = 2.70x10-7). Associations were unchanged after controlling for all genetic and environmental effects shared within families. Results from twin analyses were consistent. ‘Restriction’ (43%) and ‘pressure’ (54%) were substantially heritable, and a positive genetic correlation between child BMI and ‘restriction’ (rA = 0.28), and negative genetic correlation between child BMI and ‘pressure’ (rA = -0.48) emerged. These findings challenge the prevailing view that parental behaviours are the sole cause of child BMI by supporting an alternate hypothesis that child BMI also causes parental feeding behaviour.

Common genetic influences offer a partial explanation for comorbidity between different psychiatric disorders1,2,3. However, the genetics underlying co-development—the cross-domain co-occurrence of patterns of change over time—of psychiatric symptoms during childhood and adolescence has not been well explored. Here, we show genetic influence on joint symptom trajectories of parent-reported conduct and emotional problems (overall N = 15,082) across development (4–16 years) using both twin- and genome-wide polygenic score analyses (genotyped N = 2,610). Specifically, we found seven joint symptom trajectories, including two characterized by jointly stable and jointly increasing symptoms of conduct and emotional problems, respectively (7.3% of the sample, collectively). Twin modelling analyses revealed substantial genetic influence on trajectories (heritability estimates range of 0.41–0.78). Furthermore, individuals’ risk of being classified in the most symptomatic trajectory classes was significantly predicted by polygenic scores for years-of-education-associated alleles and depressive symptoms-associated alleles. Complementary analyses of child self-reported symptoms across late childhood and early adolescence yielded broadly similar results. Taken together, our results indicate that genetic factors are involved in the co-development of conduct and emotional problems across childhood and adolescence, and that individuals with co-developing symptoms across multiple domains may represent a clinical subgroup characterized by increased levels of genetic risk.

Objective. The transmission of anxiety within families is well-recognised, but the underlying processes are poorly understood. Twin studies of adolescent anxiety demonstrate both genetic and environmental influence, and multiple aspects of parenting are associated with offspring anxiety. To date, the Children-of-Twins design has not been used to evaluate the relative contributions of genetic versus direct transmission of anxiety from parents to their offspring. Method. Anxiety and neuroticism measures were completed by 385 monozygotic and 486 dizygotic same-sex twin families (37% male twin pair families) from the Twin and Offspring Study in Sweden (TOSS). Structural equation models tested for the presence of both genetic and environmental transmission from one generation to the next. Results. For both anxiety and neuroticism the models provide support for significant direct environmental transmission from parents to their adolescent offspring. In contrast there was no evidence of significant genetic transmission. Conclusions. The association between parental and offspring anxiety largely arises due to a direct association between parents and their children independent of genetic confounds. The lack of genetic transmission may reflect there being different genetic effects on these traits in adolescence and adulthood. Direct environmental transmission is in line with developmental theories of anxiety suggesting that children and adolescents learn anxious behaviours from their parents via a number of pathways such as modelling. Future analyses should combine children-of-twins data with child twin data in order to examine whether this direct effect solely represents parental influences on the offspring or whether it also includes child/adolescent anxiety evoking parental anxiety.

BackgroundParental depressive symptoms are associated with emotional and behavioural problems in offspring. However, genetically informative studies are needed to distinguish potential causal effects from genetic confounds, and longitudinal studies are required to distinguish parent-to-child effects from child-to-parent effects.MethodWe conducted cross-sectional analyses on a sample of Swedish twins and their adolescent offspring (n = 876 twin families), and longitudinal analyses on a US sample of children adopted at birth, their adoptive parents, and their birth mothers (n = 361 adoptive families). Depressive symptoms were measured in parents, and externalizing and internalizing problems measured in offspring. Structural equation models were fitted to the data.ResultsResults of model fitting suggest that associations between parental depressive symptoms and offspring internalizing and externalizing problems remain after accounting for genes shared between parent and child. Genetic transmission was not evident in the twin study but was evident in the adoption study. In the longitudinal adoption study child-to-parent effects were evident.ConclusionsWe interpret the results as demonstrating that associations between parental depressive symptoms and offspring emotional and behavioural problems are not solely attributable to shared genes, and that bidirectional effects may be present in intergenerational associations.

Kaprio, Jaakko/0000-0002-3716-2455; Knafo-Noam, Ariel/0000-0003-0613-1960; de Freitas, Duarte Luis/0000-0001-6642-3370; Haworth, Claire/0000-0002-8608-289X; Siribaddana, Sisira/0000-0001-5821-2557; Kyvik, Kirsten O/0000-0003-2981-0245; Aliev, Fazil/0000-0001-8357-4699; Craig, Jeffrey M/0000-0003-3979-7849; Ordonana, Juan R./0000-0001-7779-6017; Sund, Reijo/0000-0002-6268-8117; Bartels, Meike/0000-0002-9667-7555; Kandler, Christian/0000-0002-9175-235X; Fagnani, Corrado/0000-0001-5771-7772; Huibregtse, Brooke M./0000-0003-0977-7249; Montgomery, Grant W/0000-0002-4140-8139; Colodro-Conde, Lucia/0000-0002-9004-364X; Loos, Ruth J F/0000-0002-8532-5087; Busjahn, Andreas/0000-0001-9650-6919; ONCEL, Sevgi YURT/0000-0002-0990-292X; Christensen, Kaare/0000-0002-5429-5292; Martin, Nicholas/0000-0003-4069-8020; Tan, Qihua/0000-0003-3194-0030; ROMERA, JUAN FRANCISCO SANCHEZ/0000-0002-5405-6216; D'Ippolito, Cristina/0000-0001-7902-9380; Skytthe, Axel E/0000-0002-8629-4913; Tan, Qihua/0000-0003-3194-0030; Heikkila, Kauko/0000-0002-9256-8028; Duncan, Glen/0000-0001-6909-1869; Jelenkovic, Aline/0000-0002-6191-8371; Magnusson, Patrik/0000-0002-7315-7899; mangino, massimo/0000-0002-2167-7470; Medland, Sarah E/0000-0003-1382-380X; Saffery, Richard/0000-0002-9510-4181; Plomin, Robert/0000-0002-0756-3629; Harden, Kathryn/0000-0002-1557-6737; Hotopf, Matthew/0000-0002-3980-4466; McAdams, Tom/0000-0002-6825-3499; Aaltonen, Sari/0000-0002-2873-4263; Kremen, William/0000-0002-8629-5609; Pahlen, Shandell/0000-0003-0753-4155; Llewellyn, Clare/0000-0002-0066-2827; Franz, Carol/0000-0002-8987-1755; Derom, Catherine/0000-0001-5574-796X; Willemsen, Gonneke/0000-0003-3755-0236; Rasmussen, Finn/0000-0001-7915-7809; Rebato, Esther/0000-0003-1221-8501; lee, kayoung/0000-0002-2816-554X; Sodemann, Morten/0000-0001-8992-2500; Gatz, Margaret/0000-0002-1071-9970; Boivin, Michel/0000-0001-8621-9844; Silventoinen, Karri/0000-0003-1759-3079 WOS: 000358874400002 PubMed: 26014041 For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m(2)) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes. National Institute of Mental HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Mental Health (NIMH) [R01 MH58354]; National Institute on AgingUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Aging (NIA) [1RO1-AG13662-01A2]; National Institutes of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [R21 AG039572]; WT Grant Foundation; University of London Central Research fund; Medical Research CouncilMedical Research Council UK (MRC) [G81/343, G120/635]; Economic and Social Research CouncilEconomic & Social Research Council (ESRC) [RES-000-22-2206]; Institute of Social Psychiatry [06/07-11]; Leverhulme Research FellowshipLeverhulme Trust [RF/2/RFG/2008/0145]; Goldsmiths; University of London; National Research Foundation of KoreaNational Research Foundation of Korea [NRF-371-2011-1B00047]; Danish Agency for Science, Technology and Innovation; Research Council for Health and Disease; Velux Foundation; US National Institute of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [P01 AG08761]; Fund of Scientific Research, FlandersFWO; Twins, a non-profit Association for Scientific Research in Multiple Births (Belgium); Global Research Network Program of the National Research Foundation [NRF 2011-220-E00006]; NIDAUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Drug Abuse (NIDA) [DA011015]; Longitudinal Twin Study [HD10333]; National Institute of Health grantsUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [NIA R01 AG018384, R01 AG018386, R01 AG022381, R01 AG022982]; Cooperative Studies Program of the Office of Research AMP; Development of the United States Department of Veterans Affairs; Centre of Research Excellence from the National Health and Medical Research CouncilNational Health and Medical Research Council of Australia [1079102]; Michigan State University from the National Institute of Mental Health (NIMH) [R01-MH081813, R01-MH0820-54, R01-MH092377-02, R21-MH070542-01, R03-MH63851-01]; Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD) [R01-HD066040]; MSU Foundation [11-SPG-2518]; California Tobacco-Related Disease Research ProgramUniversity of California System [7RT-0134H, 8RT-0107H, 6RT-0354H]; The National Institutes of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [1R01ESO15150-01]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [81125007]; Australian National Health and Medical Research CouncilNational Health and Medical Research Council of Australia [437015, 607358]; Bonnie Babes Foundation [BBF20704]; Financial Markets Foundation for Children [032-2007]; Victorian Government's Operational Infrastructure Support Program; ENGAGE-European Network for Genetic and Genomic Epidemiology [201413]; National Institute of Alcohol Abuse and AlcoholismUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Alcohol Abuse & Alcoholism (NIAAA) [AA-12502, AA-00145, AA-09203]; Academy of Finland Center of Excellence in Complex Disease GeneticsAcademy of Finland [213506, 129680]; Academy of FinlandAcademy of Finland [100499, 205585, 118555, 141054, 265240, 263278, 264146]; Osaka University's International Joint Research Promotion Program; Kirikkale University Research Grant: KKUKirikkale University; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114C117]; European Research Council (ERC)European Research Council (ERC) [240994]; European Union's Seventh Framework Programmes ENGAGE ConsortiumEuropean Union (EU) [HEALTH-F4-2007-201413]; BioSHaRE EU [HEALTH-F4-2010-261433]; Seneca FoundationFundacion Seneca; Regional Agency for Science and Technology, Murcia, Spain [08633/PHCS/08, 15302/PHCS/10]; Ministry of Science and Innovation, SpainSpanish Government [PSI11560-2009]; UK Medical Research CouncilMedical Research Council UK (MRC) [G0901245]; UK Biotechnology and Biological Sciences Research CouncilBiotechnology and Biological Sciences Research Council (BBSRC) [31/D19086]; Portuguese agency for research (The Foundation for Science and Technology) [POCI/DES/56834/2004]; National Institutes of Health.United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [R01 HD068435, R01 MH062375]; Wellcome TrustWellcome Trust; European Community's Seventh Framework ProgrammeEuropean Union (EU); National Institute for Health Research (NIHR) BioResource Clinical Research Facility and Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London; Netherlands Organization for Scientific Research (NWO)Netherlands Organization for Scientific Research (NWO); MagW/ZonMW [904-61-090, 985-10-002, 912-10-020, 904-61-193, 480-04-004, 463-06-001, 451-04-034, 400-05-717, Addiction-31160008, Middelgroot-911-09-032, Spinozapremie 56-464-14192]; VU University's Institute for Health and Care Research (EMGO+); European Research CouncilEuropean Research Council (ERC) [ERC-230374]; Avera Institute, Sioux Falls, South Dakota (USA); Cancer Research UKCancer Research UK [C1418/A7974]; [5T32DA017637-10]; [NIH RC2 HL103416]; Cancer Research UKCancer Research UK [14133]; Medical Research CouncilMedical Research Council UK (MRC) [G0901245, MC_UU_12013/1]; NNF Center for Basic Metabolic ResearchNovo Nordisk Foundation [Metabolic Genetics]; Novo Nordisk FondenNovo NordiskNovo Nordisk Foundation [NNF10CC1016515] This study was conducted within the CODATwins project (Academy of Finland #266592). Support for participating twin projects: the University of Southern California Twin Study is funded by a grant from the National Institute of Mental Health (R01 MH58354). The Carolina African American Twin Study of Aging (CAATSA) was funded by a grant from the National Institute on Aging (grant 1RO1-AG13662-01A2) to K. E. Whitfield. The NAS-NRC Twin Registry acknowledges financial support from the National Institutes of Health grant number R21 AG039572. Waves 1-3 of Genesis 12-19 were funded by the WT Grant Foundation, the University of London Central Research fund and a Medical Research Council Training Fellowship (G81/343) and Career Development Award (G120/635) to Thalia C. Eley. Wave 4 was supported by grants from the Economic and Social Research Council (RES-000-22-2206) and the Institute of Social Psychiatry (06/07-11) to Alice M. Gregory who was also supported at that time by a Leverhulme Research Fellowship (RF/2/RFG/2008/0145). Wave 5 was supported by funding to Alice M. Gregory from Goldsmiths, University of London. Anthropometric measurements of the Hungarian twins were supported by Medexpert Ltd., Budapest, Hungary. South Korea Twin Registry is supported by National Research Foundation of Korea (NRF-371-2011-1B00047). The Danish Twin Registry is supported by the National Program for Research Infrastructure 2007 from the Danish Agency for Science, Technology and Innovation, The Research Council for Health and Disease, the Velux Foundation and the US National Institute of Health (P01 AG08761). Since its origin, the East Flanders Prospective Survey has been partly supported by grants from the Fund of Scientific Research, Flanders and Twins, a non-profit Association for Scientific Research in Multiple Births (Belgium). Korean Twin-Family Register was supported by the Global Research Network Program of the National Research Foundation (NRF 2011-220-E00006). The Colorado Twin Registry is funded by NIDA funded center grant DA011015 and Longitudinal Twin Study HD10333; Author Huibregtse is supported by 5T32DA017637-10. The Vietnam Era Twin Study of Aging was supported by National Institute of Health grants NIA R01 AG018384, R01 AG018386, R01 AG022381, and R01 AG022982, and, in part, with resources of the VA San Diego Center of Excellence for Stress and Mental Health. The Cooperative Studies Program of the Office of Research & Development of the United States Department of Veterans Affairs has provided financial support for the development and maintenance of the Vietnam Era Twin (VET) Registry. The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of the NIA/NIH, or the VA. The Australian Twin Registry is supported by a Centre of Research Excellence (grant ID 1079102) from the National Health and Medical Research Council administered by the University of Melbourne. The Michigan State University Twin Registry has been supported by Michigan State University, as well as grants R01-MH081813, R01-MH0820-54, R01-MH092377-02, R21-MH070542-01, R03-MH63851-01 from the National Institute of Mental Health (NIMH), R01-HD066040 from the Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD), and 11-SPG-2518 from the MSU Foundation. The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of the NIMH, the NICHD, or the National Institutes of Health.; r The California Twin Program was supported by The California Tobacco-Related Disease Research Program (7RT-0134H, 8RT-0107H, 6RT-0354H) and the National Institutes of Health (1R01ESO15150-01). The Guangzhou Twin Eye Study is supported by National Natural Science Foundation of China (grant #81125007). PETS was supported by grants from the Australian National Health and Medical Research Council (grant numbers 437015 and 607358 to JC, and RS), the Bonnie Babes Foundation (grant number BBF20704 to JMC), the Financial Markets Foundation for Children (grant no. 032-2007 to JMC), and by the Victorian Government's Operational Infrastructure Support Program. Data collection and analyses in Finnish twin cohorts have been supported by ENGAGE-European Network for Genetic and Genomic Epidemiology, FP7-HEALTH-F4-2007, grant agreement number 201413, National Institute of Alcohol Abuse and Alcoholism (grants AA-12502, AA-00145, and AA-09203 to R. J. Rose, the Academy of Finland Center of Excellence in Complex Disease Genetics (grant numbers: 213506, 129680), and the Academy of Finland (grants 100499, 205585, 118555, 141054, 265240, 263278 and 264146 to J. Kaprio). K. Silventoinen is supported by Osaka University's International Joint Research Promotion Program. S. Y. Oncel and F. Aliev are supported by Kirikkale University Research Grant: KKU, 2009/43 and TUBITAK grant 114C117. The Longitudinal Israeli Study of Twins was funded by the Starting Grant no. 240994 from the European Research Council (ERC) to Ariel Knafo. Data collection and research stemming from the Norwegian Twin Registry is supported, in part, from the European Union's Seventh Framework Programmes ENGAGE Consortium (grant agreement HEALTH-F4-2007-201413, and BioSHaRE EU (grant agreement HEALTH-F4-2010-261433). The Murcia Twin Registry is supported by the Seneca Foundation, Regional Agency for Science and Technology, Murcia, Spain (08633/PHCS/08 & 15302/PHCS/10) and Ministry of Science and Innovation, Spain (PSI11560-2009). The Twins Early Development Study (TEDS) is supported by a program grant (G0901245) from the UK Medical Research Council and the work on obesity in TEDS is supported in part by a grant from the UK Biotechnology and Biological Sciences Research Council (31/D19086). The Madeira data comes from the following project: genetic and environmental influences on physical activity, fitness, and health: the Madeira family study Project reference: POCI/DES/56834/2004 founded by the Portuguese agency for research (The Foundation for Science and Technology). The Boston University Twin Project is funded by grants (#R01 HD068435 #R01 MH062375) from the National Institutes of Health to K. Saudino. TwinsUK was funded by the Wellcome Trust; European Community's Seventh Framework Programme (FP7/2007-2013). The study also receives support from the National Institute for Health Research (NIHR) BioResource Clinical Research Facility and Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London. The University of Washington Twin Registry is supported by the grant NIH RC2 HL103416 (D. Buchwald, PI). The Netherlands Twin Register acknowledges the Netherlands Organization for Scientific Research (NWO) and MagW/ZonMW grants 904-61-090, 985-10-002, 912-10-020, 904-61-193,480-04-004, 463-06-001, 451-04-034, 400-05-717, Addiction-31160008, Middelgroot-911-09-032, Spinozapremie 56-464-14192; VU University's Institute for Health and Care Research (EMGO+); the European Research Council (ERC-230374), the Avera Institute, Sioux Falls, South Dakota (USA).; r Gemini was supported by a grant from Cancer Research UK (C1418/A7974).

Study Objectives Sleep quality is associated with different aspects of psychopathology, but relatively little research has examined links between sleep quality and externalizing behaviors or callous-unemotional traits. We examined: (1) whether an association exists between sleep quality and externalizing behaviors; (2) whether anxiety mediates this association; (3) whether callous-unemotional traits are associated with sleep quality. Methods Data from two studies were used. Study 1 involved 1556 participants of the G1219 study aged 18–27 years (62% female). Questionnaire measures assessed sleep quality, anxiety, externalizing behaviors, and callous-unemotional traits. Study 2 involved 338 participants aged 18–66 years (65% female). Questionnaires measured sleep quality, externalizing behaviors, and callous-unemotional traits. In order to assess objective sleep quality, actigraphic data were also recorded for a week from a subsample of study 2 participants (n = 43). Results In study 1, poorer sleep quality was associated with greater externalizing behaviors. This association was partially mediated by anxiety and moderated by levels of callous-unemotional traits. There was no significant relationship between sleep quality and callous-unemotional traits. In study 2, poorer sleep quality, as assessed via self-reported but not objective measures, was associated with higher levels of externalizing behaviors. Furthermore, in study 2, better sleep quality (indicated in both questionnaires and actigraphy measures: lower mean activity, and greater sleep efficiency) was associated with higher levels of callous-unemotional traits. Conclusions Self-reports of poorer sleep quality are associated with externalizing behaviors, and this association is partially mediated by anxiety. Callous-unemotional traits are not associated with poor sleep and may even be related to better sleep quality. This is an exceptional finding given that poor sleep quality appears to be a characteristic of most psychopathology.

BackgroundPrevious studies have found significant associations between maternal prenatal and postpartum depression and child behavior problems (CBP). The present study investigates whether associations remain in a prospective, longitudinal design adjusted for familial confounding.MethodsThe sample comprised 11,599 families including 17,830 siblings from the Norwegian Mother and Child Cohort study. Mothers reported depressive symptoms at gestational weeks 17 and 30, as well as 6 months, 1.5, 3, and 5 years postpartum. Fathers’ depression was measured at gestational week 17. At the last three time-points, child internalizing and externalizing problems were concurrently assessed. We performed multilevel analyses for internalizing and externalizing problems separately, using parental depression as predictors. Analyses were repeated using a sibling comparison design to adjust for familial confounding.ResultsAll parental depressive time-points were significantly and positively associated with child internalizing and externalizing problems. After sibling comparison, however, only concurrent maternal depression was significantly associated with internalizing [estimate = 2.82 (1.91–3.73, 95% CI)] and externalizing problems [estimate = 2.40 (1.56–3.23, 95% CI)]. The effect of concurrent maternal depression on internalizing problems increased with child age.ConclusionsOur findings do not support the notion that perinatal maternal depression is particularly detrimental to children's psychological development, as the most robust effects were found for maternal depression occurring during preschool years.

Delinquency and substance use (SU) are commonly comorbid during adolescence. In the present study we investigate this co-morbidity with 3 main objectives: 1. Evaluate reciprocal relationships between delinquency/SU across early adolescence. 2. Assess the impact of older male friends, low parental knowledge and friends' delinquency on subsequent development and inter-relationships of delinquency and SU. 3. Evaluate sex differences in these relationships. We applied cross-lagged structural equation models to the analysis of a longitudinal sample (n=3699). FINDINGS demonstrated: (1) At ages 13-14 delinquency predicted SU more so than vice versa but effects became equal between ages 14 and 15. (2) Low parental knowledge and friends' delinquency predicted delinquency and SU. Older male friends predicted ASB. (3) Sex differences were present. For example, in the absence of antisocial friends low parent knowledge at age 12 indirectly predicted increased age 15 SU for girls more than boys. Language: en

Heikkila, Kauko/0000-0002-9256-8028; McAdams, Tom/0000-0002-6825-3499; Ordonana, Juan R./0000-0001-7779-6017; Siribaddana, Sisira/0000-0001-5821-2557; Tan, Qihua/0000-0003-3194-0030; Skytthe, Axel E/0000-0002-8629-4913; Hjelmborg, Jacob/0000-0001-9630-9149; Kaprio, Jaakko/0000-0002-3716-2455; Loos, Ruth J F/0000-0002-8532-5087; ONCEL, Sevgi YURT/0000-0002-0990-292X; Fagnani, Corrado/0000-0001-5771-7772; mangino, massimo/0000-0002-2167-7470; Colodro-Conde, Lucia/0000-0002-9004-364X; Kandler, Christian/0000-0002-9175-235X; ROMERA, JUAN FRANCISCO SANCHEZ/0000-0002-5405-6216; Montgomery, Grant W/0000-0002-4140-8139; Medland, Sarah E/0000-0003-1382-380X; Christensen, Kaare/0000-0002-5429-5292; Aliev, Fazil/0000-0001-8357-4699; Huibregtse, Brooke M./0000-0003-0977-7249; Busjahn, Andreas/0000-0001-9650-6919; Tan, Qihua/0000-0003-3194-0030; Sund, Reijo/0000-0002-6268-8117; Kremen, William/0000-0002-8629-5609; Pahlen, Shandell/0000-0003-0753-4155; Rasmussen, Finn/0000-0001-7915-7809; Franz, Carol/0000-0002-8987-1755; Pedersen, Nancy/0000-0001-8057-3543; Aaltonen, Sari/0000-0002-2873-4263; Hotopf, Matthew/0000-0002-3980-4466; Rebato, Esther/0000-0003-1221-8501; Kyvik, Kirsten Ohm/0000-0003-2981-0245; Rijsdijk, Fruhling/0000-0003-4762-2803; Silventoinen, Karri/0000-0003-1759-3079 WOS: 000391277600001 PubMed: 27964777 Human height variation is determined by genetic and environmental factors, but it remains unclear whether their influences differ across birth-year cohorts. We conducted an individual-based pooled analysis of 40 twin cohorts including 143,390 complete twin pairs born 18861994. Although genetic variance showed a generally increasing trend across the birth-year cohorts, heritability estimates (0.69-0.84 in men and 0.53-0.78 in women) did not present any clear pattern of secular changes. Comparing geographic-cultural regions (Europe, North America and Australia, and East Asia), total height variance was greatest in North America and Australia and lowest in East Asia, but no clear pattern in the heritability estimates across the birth-year cohorts emerged. Our findings do not support the hypothesis that heritability of height is lower in populations with low living standards than in affluent populations, nor that heritability of height will increase within a population as living standards improve. Suomen Akatemia [266592] Suomen Akatemia 266592 Karri Silventoinenr The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Background Depression is already highly prevalent by late adolescence, indicating that research into its developmental emergence should consider earlier risk factors and environmental contexts. The home environment is a key context for children and adolescents throughout development. However, the nature of relationships that exist between aspects of the home environment and the development of depressive symptoms cannot be assumed. Genetically informative studies have been used to provide insights about the aetiology of such relationships, often finding them to be partly confounded by the influence of children's genes. Here, we investigate developmental change in the aetiology of the association between aspects of the home environment and depressive symptoms at the onset of adolescence. Methods We used longitudinal child‐ and parent‐report data from >5,000 twin pairs enrolled in the UK‐representative Twins Early Development Study. Multivariate, genetically sensitive structural equation models were used to decompose latent variance and covariance in depressive symptoms (measured at 12 and 16 years) and aspects of the home environment (at 9 and 14 years) into genetic and environmental influences. Results Going from childhood to adolescence, genetic influences accounted for an increasing proportion of the association [30% (16–42) of r = .44 in childhood; 40% (25–61) of r = .43 in adolescence], at the expense of shared environmental influences, which decreased from 70% (58–83) to 48% (29–62). Unique environmental influences accounted for a significant proportion of the association in adolescence only [12% (06–18)]. Developmental changes could largely be attributed to subtle shifts in the relative importance of stable aetiological factors, rather than the emergence of influences unique to adolescence. Conclusions These findings emphasise the importance of developmental and aetiological context in interpreting associations between aspects of the home environment and child emotional outcomes.

Loos, Ruth J F/0000-0002-8532-5087; Huibregtse, Brooke M./0000-0003-0977-7249; Busjahn, Andreas/0000-0001-9650-6919; Skytthe, Axel E/0000-0002-8629-4913; Heikkila, Kauko/0000-0002-9256-8028; Haworth, Claire/0000-0002-8608-289X; Hjelmborg, Jacob/0000-0001-9630-9149; Sund, Reijo/0000-0002-6268-8117; Aliev, Fazil/0000-0001-8357-4699; Fagnani, Corrado/0000-0001-5771-7772; Kaprio, Jaakko/0000-0002-3716-2455; Knafo-Noam, Ariel/0000-0003-0613-1960; Montgomery, Grant W/0000-0002-4140-8139; Moller, Soren/0000-0003-0858-4269; ONCEL, Sevgi YURT/0000-0002-0990-292X; Duncan, Glen/0000-0001-6909-1869; Medland, Sarah E/0000-0003-1382-380X; Kandler, Christian/0000-0002-9175-235X; Christensen, Kaare/0000-0002-5429-5292; Magnusson, Patrik/0000-0002-7315-7899; mangino, massimo/0000-0002-2167-7470; Bartels, Meike/0000-0002-9667-7555; de Freitas, Duarte Luis/0000-0001-6642-3370; Harden, Kathryn/0000-0002-1557-6737; Derom, Catherine/0000-0001-5574-796X; Plomin, Robert/0000-0002-0756-3629; Silventoinen, Karri/0000-0003-1759-3079; Rasmussen, Finn/0000-0001-7915-7809; Boivin, Michel/0000-0001-8621-9844; Saffery, Richard/0000-0002-9510-4181; Pahlen, Shandell/0000-0003-0753-4155; van Beijsterveldt, Toos/0000-0002-6617-4201; Rebato, Esther/0000-0003-1221-8501; Pedersen, Nancy/0000-0001-8057-3543; Aaltonen, Sari/0000-0002-2873-4263; Llewellyn, Clare/0000-0002-0066-2827; Kyvik, Kirsten Ohm/0000-0003-2981-0245; Sodemann, Morten/0000-0001-8992-2500; Willemsen, Gonneke/0000-0003-3755-0236; D'Ippolito, Cristina/0000-0001-7902-9380; McAdams, Tom/0000-0002-6825-3499 WOS: 000378317900001 PubMed: 27333805 Height variation is known to be determined by both genetic and environmental factors, but a systematic description of how their influences differ by sex, age and global regions is lacking. We conducted an individual-based pooled analysis of 45 twin cohorts from 20 countries, including 180,520 paired measurements at ages 1-19 years. The proportion of height variation explained by shared environmental factors was greatest in early childhood, but these effects remained present until early adulthood. Accordingly, the relative genetic contribution increased with age and was greatest in adolescence (up to 0.83 in boys and 0.76 in girls). Comparing geographic-cultural regions (Europe, North-America and Australia, and East-Asia), genetic variance was greatest in North-America and Australia and lowest in East-Asia, but the relative proportion of genetic variation was roughly similar across these regions. Our findings provide further insights into height variation during childhood and adolescence in populations representing different ethnicities and exposed to different environments. Academy of FinlandAcademy of Finland [266592, 100499, 205585, 118555, 141054, 265240, 263278, 264146]; National Institutes of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [R01 HD068435, R01 MH062375, 1R01ESO15150-01, AA023322, HD081437, R21 AG039572]; California Tobacco-Related Disease Research ProgramUniversity of California System [7RT-0134H, 8RT-0107H, 6RT-0354H]; Special Fund for Health Scientific Research in the Public Welfare, China [201502006]; NIDAUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Drug Abuse (NIDA) [DA011015, HD10333]; National Program for Research Infrastructure from the Danish Agency for Science, Technology and Innovation; Research Council for Health and Disease; Velux Foundation; US National Institute of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [P01 AG08761]; Fund of Scientific Research, Flanders and Twins; NGAGE-European Network for Genetic and Genomic Epidemiology [FP7-HEALTH-F4-2007, 201413]; National Institute of Alcohol Abuse and AlcoholismUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Alcohol Abuse & Alcoholism (NIAAA) [AA-12502, AA-00145, AA-09203]; Academy of Finland Center of Excellence in Complex Disease GeneticsAcademy of Finland [213506, 129680]; Osaka University's International Joint Research Promotion Program; Cancer Research UKCancer Research UK [C1418/A7974]; WT Grant Foundation; University of London Central Research fund; Medical Research Council Training FellowshipMedical Research Council UK (MRC) [G81/343, G120/635]; Economic and Social Research CouncilEconomic & Social Research Council (ESRC) [RES-000-22-2206]; Institute of Social Psychiatry [06/07-11]; Leverhulme Research FellowshipLeverhulme Trust [RF/2/RFG/2008/0145]; Goldsmiths, University of London; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [81125007]; Medexpert Ltd., Budapest, Hungary; European Research Council (ERC)European Research Council (ERC) [240994]; Michigan State University; National Institute of Mental Health (NIMH)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Mental Health (NIMH) [R01-MH081813, R01-MH0820-54, R01-MH092377-02, R21-MH070542-01, R03-MH63851-01]; Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD) [R01-HD066040]; MSU Foundation [11-SPG-2518]; Netherlands Organization for Scientific Research (NWO)Netherlands Organization for Scientific Research (NWO); MagW/ZonMW [904-61-090, 985-10-002, 912-10-020, 904-61-193, 480-04-004, 463-06-001, 451-04-034, 400-05-717, Addiction-31160008, Middelgroot-911-09-032, Spinozapremie 56-464-14192]; VU University's Institute for Health and Care Research (EMGO+); European Research CouncilEuropean Research Council (ERC) [ERC-230374]; Avera Institute, Sioux Falls, South Dakota (USA); Australian National Health and Medical Research CouncilNational Health and Medical Research Council of Australia [437015, 607358]; Bonnie Babes Foundation [BBF20704]; Financial Markets Foundation for Children [032-2007]; Victorian Government's Operational Infrastructure Support Program; Portuguese agency for research (The Foundation for Science and Technology [FCT]) [POCI/DES/56834/2004]; Fonds Quebecois de la Recherche sur la Societe et la CultureFQRNT; Fonds de la Recherche en Sante du QuebecFonds de la Recherche en Sante du Quebec; Social Science and Humanities Research Council of Canada; National Health Research Development Program; Canadian Institutes for Health ResearchCanadian Institutes of Health Research (CIHR); Sainte-Justine Hospital's Research Center; Canada Research Chair ProgramCanada Research Chairs; National Research Foundation of KoreaNational Research Foundation of Korea [NRF-371-2011-1 B00047]; UK Medical Research CouncilMedical Research Council UK (MRC) [G0901245]; UK Biotechnology and Biological Sciences Research CouncilBiotechnology and Biological Sciences Research Council (BBSRC) [31/D19086]; Kirikkale University Research Grant: KKUKirikkale University [2009/43]; TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114C117]; Wellcome TrustWellcome Trust; European Community's Seventh Framework Programme (FP7)European Union (EU); National Institute for Health Research (NIHR) BioResource Clinical Research Facility and Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London; National Institute of Mental HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Mental Health (NIMH) [R01 MH58354]; NIHUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USA [RC2 HL103416]; Japan Society for the Promotion of ScienceMinistry of Education, Culture, Sports, Science and Technology, Japan (MEXT)Japan Society for the Promotion of Science [15H05105]; [5T32DA017637-11]; Medical Research CouncilMedical Research Council UK (MRC) [G19/2, MR/M021475/1, G120/635, G0500079, G0901245]; NNF Center for Basic Metabolic ResearchNovo Nordisk Foundation [Metabolic Genetics]; Novo Nordisk FondenNovo NordiskNovo Nordisk Foundation [NNF10CC1016515] This study was conducted within the CODATwins project (Academy of Finland #266592). Support for participating twin projects: The Boston University Twin Project is funded by grants (#R01 HD068435 #R01 MH062375) from the National Institutes of Health to K. Saudino. California Twin Program was supported by The California Tobacco-Related Disease Research Program (7RT-0134H, 8RT-0107H, 6RT-0354H) and the National Institutes of Health (1R01ESO15150-01). Chinese National Twin Registry is funded by Special Fund for Health Scientific Research in the Public Welfare (Project No: 201502006), China. Colorado Twin Registry is funded by NIDA funded center grant DA011015, & Longitudinal Twin Study HD10333; Author Huibregtse is supported by to 5T32DA017637-11. Danish Twin Registry is supported by the National Program for Research Infrastructure 2007 from the Danish Agency for Science, Technology and Innovation, The Research Council for Health and Disease, the Velux Foundation and the US National Institute of Health (P01 AG08761). Since its origin the East Flanders Prospective Survey has been partly supported by grants from the Fund of Scientific Research, Flanders and Twins, a non-profit Association for Scientific Research in Multiple Births (Belgium). Data collection and analyses in Finnish twin cohorts have been supported by ENGAGE-European Network for Genetic and Genomic Epidemiology, FP7-HEALTH-F4-2007, grant agreement number 201413, National Institute of Alcohol Abuse and Alcoholism (grants AA-12502, AA-00145, and AA-09203 to RJ Rose, the Academy of Finland Center of Excellence in Complex Disease Genetics (grant numbers: 213506, 129680), and the Academy of Finland (grants 100499, 205585, 118555, 141054, 265240, 263278 and 264146 to J. Kaprio). K. Silventoinen is supported by Osaka University's International Joint Research Promotion Program. Gemini was supported by a grant from Cancer Research UK (C1418/A7974). Waves 1-3 of Genesis 12-19 were funded by the WT Grant Foundation, the University of London Central Research fund and a Medical Research Council Training Fellowship (G81/343) and Career Development Award (G120/635) to Thalia C. Eley. Wave 4 was supported by grants from the Economic and Social Research Council (RES-000-22-2206) and the Institute of Social Psychiatry (06/07-11) to Alice M. Gregory who was also supported at that time by a Leverhulme Research Fellowship (RF/2/RFG/2008/0145). Wave 5 was supported by funding to Alice M. Gregory from Goldsmiths, University of London. Guangzhou Twin Eye Study is supported by National Natural Science Foundation of China (grant #81125007). Anthropometric measurements of the Hungarian twins were supported by Medexpert Ltd., Budapest, Hungary. Longitudinal Israeli Study of Twins was funded by the Starting Grant no. 240994 from the European Research Council (ERC) to Ariel Knafo. The Michigan State University Twin Registry has been supported by Michigan State University, as well as grants R01-MH081813, R01-MH0820-54, R01-MH092377-02, R21-MH070542-01, R03-MH63851-01 from the National Institute of Mental Health (NIMH), R01-HD066040 from the Eunice Kennedy Shriver National Institute for Child Health and Human Development (NICHD), and 11-SPG-2518 from the MSU Foundation. The content of this manuscript is solely the responsibility of the authors and does not necessarily represent the official views of the NIMH, the NICHD, or the National Institutes of Health. The NAS-NRC Twin Registry acknowledges financial support from the National Institutes of Health grant number R21 AG039572.; Netherlands Twin Register acknowledges the Netherlands Organization for Scientific Research (NWO) and MagW/ZonMW grants 904-61-090, 985-10-002, 912-10-020, 904-61-193,480-04-004, 463-06-001, 451-04-034, 400-05-717, Addiction-31160008, Middelgroot-911-09-032, Spinozapremie 56-464-14192; VU University's Institute for Health and Care Research (EMGO+); the European Research Council (ERC-230374), the Avera Institute, Sioux Falls, South Dakota (USA). PETS was supported by grants from the Australian National Health and Medical Research Council (grant numbers 437015 and 607358 to J. C. and R.S.), the Bonnie Babes Foundation (grant number BBF20704 to J. M. C.), the Financial Markets Foundation for Children (grant no. 032-2007 to J. M. C.), and by the Victorian Government's Operational Infrastructure Support Program. Madeira data comes from the following project: Genetic and environmental influences on physical activity, fitness and health: the Madeira family study Project reference: POCI/DES/56834/2004 Founded by the Portuguese agency for research (The Foundation for Science and Technology [FCT]). The Quebec Newborn Twin Study acknowledges financial support from the Fonds Quebecois de la Recherche sur la Societe et la Culture, the Fonds de la Recherche en Sante du Quebec, the Social Science and Humanities Research Council of Canada, the National Health Research Development Program, the Canadian Institutes for Health Research, Sainte-Justine Hospital's Research Center, and the Canada Research Chair Program (Michel Boivin). South Korea Twin Registry is supported by National Research Foundation of Korea (NRF-371-2011-1 B00047). The Texas Twin Project is currently funded by grants AA023322 and HD081437 from the National Institutes of Health. The Twins Early Development Study (TEDS) is supported by a program grant (G0901245) from the UK Medical Research Council and the work on obesity in TEDS is supported in part by a grant from the UK Biotechnology and Biological Sciences Research Council (31/D19086). S.Y. Oncel and F. Aliev are supported by Kirikkale University Research Grant: KKU, 2009/43 and TUBITAK grant 114C117. TwinsUK was funded by the Wellcome Trust; European Community's Seventh Framework Programme (FP7/2007-2013). The study also receives support from the National Institute for Health Research (NIHR) BioResource Clinical Research Facility and Biomedical Research Centre based at Guy's and St Thomas' NHS Foundation Trust and King's College London. The University of Southern California Twin Study is funded by a grant from the National Institute of Mental Health (R01 MH58354). Washington State Twin Registry (formerly the University of Washington Twin Registry) was supported in part by grant NIH RC2 HL103416 (D. Buchwald, PI). The West Japan Twins and Higher Order Multiple Births Registry was supported by Grant-in-Aid for Scientific Research (B) (grant number 15H05105) from the Japan Society for the Promotion of Science.

Background Low self‐worth during adolescence predicts a range of emotional and behavioural problems. As such, identifying potential sources of influence on self‐worth is important. Aspects of the parent–child relationship are often associated with adolescent self‐worth but to date it is unclear whether such associations may be attributable to familial confounding (e.g. genetic relatedness). We set out to clarify the nature of relationships between parental expressed affection and adolescent self‐worth, and parent–child closeness and adolescent self‐worth. Methods We used data from the Twin and Offspring Study in Sweden, a children‐of‐twins sample comprising 909 adult twin pairs with adolescent children. Using these data we were able to apply structural equation models with which we could examine whether associations remained after accounting for genetic transmission. Results Results demonstrated that parent–child closeness and parental‐expressed affection were both phenotypically associated with adolescent self‐worth. Associations could not be attributed to genetic relatedness between parent and child. Conclusions Parent–child closeness and parental affection are associated with adolescent self‐worth above and beyond effects attributable to genetic relatedness. Data were cross‐sectional, so the direction of effects cannot be confirmed but findings support the notion that positive parent–child relationships increase adolescent self‐worth.