Search

Background: Due to different assessment modes employed, a clear picture of the prevalence of sleep bruxism across time cannot be formed. Moreover, studies on the persistent or fluctuating nature of sleep bruxism have yielded divergent and even contradictory results. The aim of the present study was to evaluate in a nationwide twin cohort whether self‐reported sleep bruxism was correlated longitudinally, pairwise and cross‐twin over a 20‐year period. Objectives: Self‐reported bruxism was assessed in 1990 and 2011 by mailed questionnaires in the Finnish Twin Cohort study of same‐sex twins born 1945–1957. Methods: We assessed the phenotypic stability over time for all participating individuals (n = 4992). Among zygosity verified pairs (n = 516 MZ and n = 837 DZ), we estimated the cross‐sectional zygosity correlations and the zygosity‐specific cross‐twin cross‐time correlations. Results: Reported bruxism appeared rather persistent over time without significant difference regarding zygosity. The overall phenotypic longitudinal correlation was 0.540 and somewhat higher in men (0.596) than in women (0.507). Pairwise trait correlations in 1990 and 2011 were higher in MZ than in DZ pairs. The cross‐twin cross‐time correlations were higher in MZ twins than in DZ twins, but less than the cross‐sectional MZ and DZ pairwise correlations. Conclusions: The higher correlation of reported sleep bruxism in the cross‐twin cross‐time analyses in MZ than in DZ pairs implies a genetic background for bruxism persistence. Also, bruxism over time in individual twins appears to be fairly persistent and somewhat higher in men than women. [ABSTRACT FROM AUTHOR]

Objective: Eating disorders are associated with subsequent alcohol problems, but it is not known whether this association also extends to broader eating disorder symptoms not captured by clinical diagnoses. We assessed the longitudinal association of broad eating disorder symptoms with alcohol problems in a nationwide twin sample (FinnTwin16). Methods: Finnish women (N = 1905) and men (N = 1449) self‐reported their eating disorder symptoms using the Eating Disorder Inventory‐2 Bulimia, Drive for Thinness, and Body Dissatisfaction subscales at the mean age of 24.4 years in 2000–2003. A subsample of participants also completed items on drive for muscularity, height dissatisfaction, and muscle‐enhancing supplement use. Alcohol problems were assessed 10 years later at the age of 34.1 in 2010–2012 with the Rutgers Alcohol Problem Index. Results: Eating disorder symptoms were associated with later alcohol problems (odds ratio per point increase 1.02–1.18). Bulimia showed stronger associations among men than women (p for interaction.012). Drive for muscularity and height dissatisfaction were also associated with later alcohol problems, but supplement use was not. When accounting for baseline alcohol problems, only Bulimia (among women and men) and Drive for Thinness (among men) were significantly associated with later alcohol problems. Bulimia was also significantly associated with later alcohol problems in within‐twin‐pair analyses among dizygotic twins, but not among monozygotic twins. Discussion: In a longitudinal setting, eating disorder symptoms were associated with later alcohol problems. Bulimic symptoms were a stronger risk factor for men than women. These associations may be attributable to baseline alcohol problems, childhood environment and genetic liability. Public significance: This study found that both young adult women and men with broad eating disorder symptoms are at a higher risk of alcohol‐related problems than those without such symptoms. Men with bulimic symptoms were at a particularly high risk. These findings emphasize the need for better prevention and treatment of disordered eating, body image concerns and alcohol problems for both young adult women and men. [ABSTRACT FROM AUTHOR]

The article discusses research which found that smoking cessation is not associated with a decline in reported sleep bruxism in middle-aged Finnish twins. The study considered the role of environmental factors in the aetiology of sleep bruxism. It used Chi-square test to analyze the bruxism status of Finnish twins in 2011 and whether smoking cessation during 1990-2011 was associated with it.

Genetic and early environmental differences including early health habits associate with future health. To provide insight on the causal nature of these associations, monozygotic (MZ) twin pairs discordant for health habits provide an interesting natural experiment. Twin pairs discordant for leisure‐time physical activity (LTPA) in early adult life is thus a powerful study design to investigate the associations between long‐term LTPA and indicators of health and wellbeing. We have identified 17 LTPA discordant twin pairs from two Finnish twin cohorts and summarize key findings of these studies in this paper. The carefully characterized rare long‐term LTPA discordant MZ twin pairs have participated in multi‐dimensional clinical examinations. Key findings highlight that compared with less active twins in such MZ twin pairs, the twins with higher long‐term LTPA have higher physical fitness, reduced body fat, reduced visceral fat, reduced liver fat, increased lumen diameters of conduit arteries to the lower limbs, increased bone mineral density in loaded bone areas, and an increased number of large high‐density lipoprotein particles. The findings increase our understanding on the possible site‐specific and system‐level effects of long‐term LTPA. [ABSTRACT FROM AUTHOR]

Background: Do drinking patterns in late adolescence/early adulthood predict lifetime childlessness and number of children? Research on this question has been only tangentially relevant and the results inconsistent. The designs used to date have been compromised by genetic and environmental confounds that are poorly controlled; covariate effects of smoking and education that are often ignored; males being understudied; population‐based sampling rare, and long‐term prospective studies with genetically informative designs yet to be reported. Method: In a 33‐year follow‐up, we linked the drinking patterns of >3500 Finnish twin pairs, assessed at ages 18–25, to registry data on their eventual number of children. Analyses distinguished associations of early drinking patterns with lifetime childlessness from those predictive of family size. Within‐twin pair analyses used fixed‐effects regression models to account for shared familial confounds and genetic liabilities. Childlessness was analyzed with Cox proportional hazards models and family size with Poisson regression. Analyses within‐pairs and of twins as individuals were run before and after adjustment for smoking and education, and for oral contraceptive (OC) use in individual‐level analyses of female twins. Results: Baseline abstinence and heavier drinking both significantly predicted lifetime childlessness in individual‐level analyses. Few abstinent women used OCs, but they were nonetheless more often eventually childless; adjusting for smoking and education did not affect this finding. Excluding childless twins, Poisson models of family size showed heavier drinking at 18–25 to be predictive of fewer children in both men and women. Those associations were replicated in within‐pair analyses of dizygotic twins, each level of heavier drinking being associated with smaller families. Among monozygotic twins, associations of drinking with completed family size yielded effects of similar magnitude, reaching significance at the highest levels of consumption, ruling out familial confounds. Conclusions: Compared to moderate levels of drinking, both abstinence and heavier drinking in late adolescence/early adulthood predicted a greater likelihood of lifetime childlessness and eventual number of children. Familial confounds do not fully explain these associations. [ABSTRACT FROM AUTHOR]

Introduction: Although the perinatal mortality of monochorionic twins has been reported to be higher, the role of chorionicity is debated and data from Finland are still lacking. To examine the effect of chorionicity on the main outcome measures, perinatal and neonatal mortality and neonatal morbidity of Finnish twins, a comprehensive population‐based historical cohort study was performed at Helsinki University Hospitals. Material and methods: All 1034 dichorionic and monochorionic‐diamniotic twin pregnancies managed at Helsinki University Hospital area during 2006, 2010, 2014 and 2018 were collected from patient databases. Information on chorionicity was retrieved from ultrasound reports and all relevant clinical information from patient records. Differences in perinatal and neonatal mortality and neonatal morbidity were analyzed by performing group comparisons between the twins and chorionicity. The role of chorionicity was also assessed in logistic regression analyses. Results: There were 1034 dichorionic‐diamniotic (DCDA, n = 789, 76.3%, 95% confidence interval [CI] 73.6–78.9) and monochorionic‐diamniotic (MCDA, n = 245, 23.7%, 95% CI 21.4–26.0) twin pregnancies during the studied years. Most (n = 580, 56.1%, 95% CI 52.8–59.2) twins were born at term, but 151 (61.6%, 95% CI 55.8–67.3) of MCDA twins were preterm and had lower birthweight and Apgar scores and higher risk of death of one twin. Perinatal and neonatal mortality did not differ between twins A and B, but the immediate outcome of twin B was worse, with lower arterial pH and Apgar scores and increased need of neonatal intensive care unit treatment. Conclusions: Chorionicity contributes to the perinatal and neonatal outcome in favor of dichorionic twins. This disadvantage of MCDA twinning is likely explained by earlier gestational age at birth and inequal placental sharing. Irrespective of chorionicity, twin B faces more complications. [ABSTRACT FROM AUTHOR]

Aims: To investigate how strongly smoking dependence and smoking dependence motives are associated with depressive symptoms among daily smokers and if these associations are independent of measured confounders and shared familial factors. Design Cross‐sectional individual‐based and within‐pair analyses. Setting: Fourth wave of the population‐based Finnish Twin Cohort conducted in 2011. Participants: 918 daily smokers born 1945–1957 (48% men), mean age 59.5 years including 38 twin pairs discordant for depression. Measurements Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression scale with a cut off value ≥20 for depression. Smoking dependence was assessed using the Fagerström Test for Cigarette Dependence (FTCD) and smoking dependence motives with three subscales from the multi‐dimensional Brief Wisconsin Inventory of Smoking Dependence Motives (WISDM): primary dependence motives (PDM), affective enhancement (AE), and Taste. Logistic regressions, using standardized scores of independent variables and adjusted for multiple confounders with correction for sampling as twin pairs, were used in the individual‐based analyses. Conditional logistic regression was used to control for shared familial factors in discordant twin pairs. Findings Prevalence of depression was 18% (n = 163: 61 [14%] in men, n = 102 [22%] in women). Higher smoking dependence measured by the FTCD (OR 1.45; 95% CI 1.20, 1.75), and dependence motives measured by the PDM (1.56; 1.30, 1.87) and the AE (1.54; 1.28, 1.85) were associated with higher odds of depression. The associations remained after adjusting for individual confounders, except for neuroticism, which attenuated all associations. FTCD, PDM, and AE showed associations with depression within depression‐discordant monozygotic pairs, suggesting an association independent of familial factors. Conclusions: Depression appears to be associated with smoking dependence and smoking dependence motives related to heavy, automatic use and use to regulate affective states. The associations appear to be confounded or mediated by neuroticism but are independent of shared familial influences. [ABSTRACT FROM AUTHOR]

Background: DNA methylation may play a role in the progression from normative to problematic drinking and underlie adverse health outcomes associated with alcohol misuse. We examined the association between alcohol consumption and DNA methylation patterns using 3 approaches: a conventional epigenome‐wide association study (EWAS); a co‐twin comparison design, which controls for genetic and environmental influences that twins share; and a regression of age acceleration, defined as a discrepancy between chronological age and DNA methylation age, on alcohol consumption. Methods: Participants came from the Finnish Twin Cohorts (FinnTwin12/FinnTwin16; N = 1,004; 55% female; average age = 23 years). Individuals reported the number of alcoholic beverages consumed in the past week, and epigenome‐wide DNA methylation was assessed in whole blood using the Infinium HumanMethylation450 BeadChip. Results: In the EWAS, alcohol consumption was significantly related to methylation at 24 CpG sites. When evaluating whether differences between twin siblings (185 monozygotic pairs) in alcohol consumption predicted differences in DNA methylation, co‐twin comparisons replicated 4 CpG sites from the EWAS and identified 23 additional sites. However, when we examined qualitative differences in drinking patterns between twins (heavy drinker vs. light drinker/abstainer or moderate drinker vs. abstainer; 44 pairs), methylation patterns did not significantly differ within twin pairs. Finally, individuals who reported higher alcohol consumption also exhibited greater age acceleration, though results were no longer significant after controlling for genetic and environmental influences shared by co‐twins. Conclusions: Our analyses offer insight into the associations between epigenetic variation and levels of alcohol consumption in young adulthood. [ABSTRACT FROM AUTHOR]

Background and Aims: Previous twin research suggests relationship status can moderate underlying genetic liability towards alcohol misuse. This paper examined: (1) whether genome‐wide polygenic scores (GPS) for alcohol consumption are associated with alcohol misuse; (2) whether these GPS are moderated by romantic relationships (gene–environment interaction; G × E) and (3) whether G × E results are consistent across sex. Design: Linear mixed‐effects models were used to test associations between genome‐wide polygenic scores, relationship status and alcohol use/misuse. Setting: Finnish twins born between 1983 and 1987 identified through Finland's central population registry. Participants: An intensively studied subset of Finnish Twin Study (FinnTwin12) during the young adult phase (aged 20–26 years). The analytical sample includes those with complete interview and genetic data (n = 1201). Measurements Key measurements included involvement in a romantic partnership, drinking frequency, intoxication frequency and DSM‐IV alcohol dependence (AD) symptoms. Genome‐wide polygenic scores (GPS) were created from available summary statistics from a large genome‐wide association study (GWAS) of drinks per week. Results: GPS predicted drinking frequency [b = 0.109; 95% confidence interval (CI) = 0.050, 0.168], intoxication frequency (b = 0.111; 95% CI = 0.054, 0.168) and AD symptoms (b = 0.123; 95% CI = 0.064, 0.182). Having a romantic relationship negatively influenced the association between GPS and drinking frequency (b = −0.105; 95% CI = −0.211, −0.001), intoxication frequency (b = −0.118; 95% CI = −0.220, −0.016) and AD symptoms (b = −0.119; 95% CI = −0.229, −0.009). There was a three‐way interaction between sex, relationship status and GPS for intoxication frequency (b = 0.223; 95% CI = 0.013, 0.433), such that the reduced association between GPS and intoxication frequency for those in a relationship was only apparent in males. We found no evidence of three‐way interactions for drinking frequency or AD symptoms. Conclusions: Being in a romantic relationship reduced the association between genetic predisposition and drinking, high‐risk drinking and alcohol problems. However, for high‐risk drinking the protective effect was limited to males, mapping onto earlier findings suggesting that males benefit more from romantic partnerships. [ABSTRACT FROM AUTHOR]

Aims: To estimate birth cohort effects on alcohol consumption and abstinence in Finland and to test differences between birth cohorts in genetic and environmental sources of variation in Finnish adult alcohol use. Design The Older Finnish Twin Cohort longitudinal survey study 1975–2011. Setting: Finland. Participants: A total of 26 121 same‐sex twins aged 18–95 years (full twin pairs at baseline n = 11 608). Measurements Outcome variables were the quantity of alcohol consumption (g/month) and abstinence (drinking zero g/month). Predictor variables were 10‐year birth cohort categories and socio‐demographic covariates. In quantitative genetic models, two larger cohorts (born 1901–20 and 1945–57) were compared. Findings: Multi‐level models in both sexes indicated higher levels of alcohol consumption in more recent birth cohorts and lower levels in earlier cohorts, compared with twins born 1921–30 (all P < 0.003). Similarly, compared with twins born 1921–30, abstaining was more common in earlier and less common in more recent cohorts (all P < 0.05), with the exception of men born 1911–20. Birth cohort differences in the genetic and environmental variance components in alcohol consumption were found: heritability was 21% [95% confidence interval (CI) = 0–56%] in the earlier‐born cohort of women [mean age 62.8, standard deviation (SD) = 5.3] and 51% (95% CI = 36–56%) in a more recent cohort (mean age 60.2, SD = 3.7) at the age of 54–74. For men, heritability was 39% (95% CI = 27–45%) in both cohorts. In alcohol abstinence, environmental influences shared between co‐twins explained a large proportion of variation in the earlier‐born cohort (43%, 95% CI = 23–63%), whereas non‐shared environmental (54%, 95% CI = 39–72%) and additive genetic influences (40%, 95% CI = 13–61%) were more important among more recent cohorts of men and women. Conclusion: The contribution of genetic and environmental variability to variability in alcohol consumption in the Finnish population appears to vary by birth cohort. [ABSTRACT FROM AUTHOR]

Twin studies have estimated the relative contribution of genes and the environment to variance in exercise behavior and it is known that parental education positively affects exercise levels. This study investigates the role of parental education as a potential modifier of variance in exercise behavior from age 7 to 18 years. The study is based on large datasets from the Netherlands Twin Register ( NTR: N = 24 874 twins; surveys around the ages of 7, 10, 12, 14, 16 and 18 years) and two Finnish twin cohorts ( FinnTwin12: N = 4399; 12, 14 and 17 years; FinnTwin16: N = 4648; 16, 17 and 18 years). Regular participation in moderate-to-vigorous exercise activities during leisure time was assessed by survey. Parental education was dichotomized ('both parents with a low education' vs 'at least one parent with a high education'). The mean in exercise behavior tended to be higher and the variance tended to be lower in children of high educated parents. Evidence for gene-by-environment interaction was weak. To develop successful interventions that specifically target children of low educated parents, the mechanisms causing the mean and variance differences between the two groups should be better understood. [ABSTRACT FROM AUTHOR]

Purpose:The benefits of physical activity (PA) in preventing abdominal obesity are well recognized, but the role of different sport disciplines remains open. We aimed, therefore, to investigate how participation in different sport disciplines, and the number and types of sports engaged in are associated with waist circumference (WC) in young adulthood.Methods:This population-based cohort study comprised 4027 Finnish twin individuals (1874 men), with a mean age of 34 y (32–37), who answered a survey, including self-measured WC. We extracted the number and identified the types (aerobic, power, and mixed) of the different sport disciplines respondents reported participating in.Results:The number of sport disciplines participated in was inversely associated with WC, the linear decrease averaging 1.38 cm (95% CI 1.10–1.65) per each additional sport discipline. The result persisted after adjustment for the main covariates, such as volume of PA and diet quality. Among dizygotic twin pairs discordant for sports participation (0–2 vs. 5 or more disciplines), the mean within-pair difference in WC was 4.8 cm (95% CI 0.4–9.1) for men and 11.2 cm (95% CI 4.4–18.0) for women; among discordant monozygotic pairs, no differences were observed. In men, all three types of sports were individually associated with smaller WC, while in women, only mixed and power sports showed this association.Conclusions:Participation in several sport disciplines and sport types was associated with smaller WC among young adults in their mid-30s. Shared genetic background may explain some of the associations. [ABSTRACT FROM PUBLISHER]

Introduction: The main aims of this study were to compare maternal and neonatal outcomes in term twin birth according to the planned mode of delivery and to study the effects of chorionicity and inter-twin delivery time on neonatal outcome.Material and Methods: A single-center cohort study of 495 women with twin deliveries at ≥37+0 weeks of gestation. Term twin deliveries were divided into a trial of labor group (TOL, 69.3%) and a planned cesarean section (CS) group (30.7%). The primary outcomes were maternal and neonatal morbidity.Results: 80.8% of women attempting TOL achieved vaginal birth. In the TOL group, mothers had less bleeding [median 500 mL (range 150-2700 mL) vs. 950 mL (range 150-3500 mL), p < 0.001) and fewer surgical complications (3.2% vs. 8.6%, p = 0.011), whereas second twins more often had five-minute Apgar scores of <7 (5.0% vs. 0%, p = 0.002) or umbilical artery pH < 7.05 (5.7% vs. 0%, p = 0.003), compared with the planned CS group. There was a slight, non-significant tendency for more NICU admissions in the TOL group, yet the need for NICU treatment was infrequent in the whole study material. Outcomes among dichorionic (DC) second twins were similar to those in the whole material, but among monochorionic (MC) second twins there were no differences between the TOL and planned CS groups. In secondary analysis, a five-minute Apgar score <7 occurred significantly more often in the DC group among second twins if the inter-twin delivery time exceeded 30 min.Conclusions: TOL is a good option for women with twin pregnancy at term, regardless of chorionicity. Active management of labor for the second twin is important, also in DC births. Maternal outcomes were more favorable with TOL and although low Apgar scores and low umbilical blood pH may be more frequent after TOL - especially with the second twin - serious neonatal morbidity is rare and does not differ from that after planned CS. [ABSTRACT FROM AUTHOR]

Since medieval times, an association between religiosity and anorexia nervosa has been suggested, but few systematic studies exist. This study examines in a nationwide setting whether personal or family religiosity is associated with lifetime anorexia nervosa among women in adolescence and early adulthood. Women ( N = 2,825) from the 1975 to 1979 birth cohorts of Finnish twins were screened for lifetime DSM-5 anorexia nervosa ( N = 92). Parental religiosity was assessed by self-report when the women were aged 16 years. The women self-reported their religiosity at ages 16 and 22 to 27 years. Parental religiosity did not increase the risk of lifetime anorexia nervosa, and neither did religiosity of the women themselves in adolescence. In early adulthood, a J-shaped curve was compatible with the data, indicating increased risk both at low and high levels of religiosity, but this result was statistically non-significant. Religiosity was weakly negatively correlated with body dissatisfaction. There was some suggestive evidence for socioregional variation in the association of religiosity with lifetime anorexia nervosa. In this first population study to directly address religiosity and anorexia nervosa, no evidence was found for a significant association of religiosity with anorexia nervosa either at the personal or family level. Some regional differences are possible. A modest protective association of religiosity with body dissatisfaction is also possible. Despite compelling case descriptions of 'holy anorexia,' religiosity does not appear to be a central factor in the development of anorexia nervosa in Finland, a highly secularized Christian country. [ABSTRACT FROM AUTHOR]

ABSTRACT Objective To examine the occurrence, course, and clinical picture of the DSM-5 residual categories 'Other Specified Feeding or Eating Disorder' (OSFED) and 'Unspecified Feeding or Eating Disorder' (UFED), to describe potential subtypes, and to evaluate whether the subdivision of the residual category appears meaningful. Method We screened women from the 1975-79 birth cohorts of Finnish twins ( N = 2825) for lifetime eating disorders using questionnaires and the SCID interview. This analysis characterizes women who reported clinically significant eating disorder symptoms but did not fulfill diagnostic criteria for DSM-5 anorexia nervosa (AN), bulimia nervosa (BN), or binge eating disorder (BED). Results Thirty-eight women (21% of those with an eating disorder) fell in the residual OSFED/UFED category. A third of them ( N = 14) fulfilled OSFED criteria, whereas two thirds ( N = 24) fell in the UFED category. The lifetime prevalence of OSFED/UFED was 1.5% (95% CI 1.1-2.0%), less than half of the prevalence of DSM-IV eating disorder not otherwise specified (EDNOS). The mean age of onset of OSFED/UFED was 18 years, median duration of symptoms was two years, and the 5-year probability of recovery was 60%. Over a third of women with OSFED/UFED suffered from comorbid psychiatric disorders. Both residual categories were clinically heterogeneous and included atypical forms of AN, BN, and BED. Conclusions Applying the DSM-5 criteria in a community sample of young women more than halved the occurrence of residual eating disorder diagnoses, but resulted in two instead of one clinically heterogeneous residual categories. Nevertheless, residual eating disorders were associated with considerable clinical severity. © 2016 Wiley Periodicals, Inc. (Int J Eat Disord 2016; 49:1010-1017) [ABSTRACT FROM AUTHOR]

Aims To determine (1) the prospective associations of conduct problems during early adolescence with tobacco, alcohol and cannabis use in young adulthood and (2) to what extent these associations are due to overlapping genetic versus environmental influences. Design A prospective twin study using biometric twin modelling. Setting Finland. Participants A total of 1847 Finnish twins (943 males and 904 females) were interviewed in early adolescence, 73% of whom ( n = 1353, 640 males and 713 females) were retained in young adulthood. Measurements Symptom counts of conduct disorder (CD) criteria were obtained from a semi-structured clinical interview in early adolescence [age 14-15 years, mean = 14.2, standard deviation (SD) = 0.15]. Frequency of alcohol, tobacco and cannabis use was obtained from a semi-structured clinical interview in young adulthood (age 19.9-26.6 years, mean = 22.4, SD = 0.7). Findings We found modest to moderate phenotypical correlations ( r = 0.16-0.35) between early adolescent CD symptoms and substance use in young adulthood. In males, the phenotypical correlations of CD symptoms with all three substance use variables are explained largely by overlapping genetic influences. In females, overlapping shared environmental influences predominantly explain the phenotypical correlation between CD symptoms and tobacco and cannabis use. Conclusions Conduct disorder symptoms in early adolescence appear to moderately predict substance use in early adulthood. In males, genetic influences seem to be most important in explaining the relationship between conduct disorder symptoms and substance use whereas in females, shared environmental influences seem to be most important. [ABSTRACT FROM AUTHOR]

ABSTRACT Objective Eating disorders and alcohol use disorders often co-occur, but few prospective studies have examined their relationship. Using a large population-based twin sample, we investigated how the drinking behaviors of women with lifetime eating disorders unfold from adolescence to adulthood. Method We identified 182 women with a lifetime eating disorder assessed at mean age 24, including 92 women with DSM-5 anorexia nervosa and 58 women with DSM-5 bulimia nervosa, from the 1975-1979 birth cohorts of Finnish twins ( N = 2,825 women). Frequency of drinking and intoxicating were assessed at ages 16, 24, and 34. Drinking problems were assessed at ages 24 and 34 by the Malmö-modified Michigan Alcohol Screening Test (Mm-Mast) and the Rutgers Alcohol Problem Index (RAPI). Results At age 16, proportionately more women with eating disorders reported being severely intoxicated when they last drank (25% vs.16%, P = 0.001), and at both surveys in adulthood, they reported more frequent intoxication and more alcohol-related problems than their unaffected peers. Those who had recovered from their eating disorder at age 24 still reported more alcohol-related problems in their 30s than did other women. The age of drinking onset, number of monthly drinking days, or frequency of intoxication in adolescence did not differ between women with lifetime eating disorders and unaffected women. Discussion Women with eating disorders scored higher than their unaffected peers on scales measuring alcohol dependence, alcohol-related problems, and intoxication. These differences persisted from mid-adolescence into young adulthood. Women with eating disorders should be assessed routinely for drinking behaviors. © 2016 Wiley Periodicals, Inc. (Int J Eat Disord 2016; 49:563-571) [ABSTRACT FROM AUTHOR]

Aims To determine if associations of alcohol consumption with all-cause mortality replicate in discordant monozygotic twin comparisons that control for familial and genetic confounds. Design A 30-year prospective follow-up. Setting Population-based older Finnish twin cohort. Participants Same-sex twins, aged 24-60 years at the end of 1981, without overt comorbidities, completed questionnaires in 1975 and 1981 with response rates of 89 and 84%. A total of 15 607 twins were available for mortality follow-up from the date of returned 1981 questionnaires to 31 December 2011; 14 787 twins with complete information were analysed. Measurements Self-reported monthly alcohol consumption, heavy drinking occasions (HDO) and alcohol-induced blackouts. Adjustments for age, gender, marital and smoking status, physical activity, obesity, education and social class. Findings Among twins as individuals, high levels of monthly alcohol consumption (≥ 259 g/month) associated with earlier mortality [hazard ratio (HR) = 1.63, 95% confidence interval (CI) = 1.47-1.81]. That association was replicated in comparisons of all informatively drinking-discordant twin pairs (HR = 1.91, 95% CI = 1.49-2.45) and within discordant monozygotic (MZ) twin pairs (HR = 2.24, 95% CI = 1.31-3.85), with comparable effect size. Smaller samples of MZ twins discordant for HDO and blackouts limited power; a significant association with mortality was found for multiple blackouts (HR = 2.82, 95% CI = 1.30-6.08), but not for HDO. Conclusions The associations of high levels of monthly alcohol consumption and alcohol-induced blackouts with increased all-cause mortality among Finnish twins cannot be explained by familial or genetic confounds; the explanation appears to be causal. [ABSTRACT FROM AUTHOR]

Objective: To assess the population prevalence and incidence of binge eating disorder (BED) among young women. Method: In a nationwide longitudinal study of Finnish twins born 1975-1979, the women participated in five surveys from age 16 until their mid-thirties. At Wave 4 (mean age 24 years), the women (N52,825) underwent a 2-stage screening for eating disorders. We assessed the lifetime prevalence, incidence, and clinical characteristics of DSM-5 BED. Results: We detected 16 women who met DSM-5 criteria for BED, yielding a lifetime prevalence of 0.7% (95% confidence interval [CI] 0.4-1.2%). The incidence of BED among women between 10 and 24 years of age was 35 (95% CI 20-60) per 100,000 person-years. The mean age of onset of BED was 19 years (range 13-27 years). Of the cases, 13/16 (81%) were currently ill. Duration of illness at the time of assessment ranged from less than a year to 13 years (median 6 years). Of women with BED, only two had a history of other eating disorders, but six had lifetime major depressive disorder. Two-thirds of the women with BED belonged to the highest weight quartile at age 16, and their mean BMI at age 22-27 year was 26.2 kg/m² (range 22.1-32.5 kg/m²). Discussion: Incident BED as defined by DSM-5 was relatively rare among younger women and was often preceded by relative overweight. BED often occurred without a history of other eating disorders, but comorbidity with major depressive disorder was common. [ABSTRACT FROM AUTHOR]

ABSTRACT Objective Few studies have assessed outcomes of anorexia nervosa (AN) outside clinical settings. We aimed to assess mortality, recovery, and socio-demographic outcomes of AN in a community sample. Method Women in the nationwide FinnTwin16 cohort (born 1975-1979) were followed for 10 years after baseline diagnostic assessment (mean age at follow-up 34 years, N = 2188). We compared women with lifetime DSM-IV AN ( N = 40) with unaffected women from the same cohort. Results None of the women with AN had died and 88% were weight-recovered (BMI ≥ 18.5 kg/m2), but their mean BMI (22.0 kg/m2) was lower than among unaffected women (24.0 kg/m2, p = 0.008). University degrees (38 vs. 29%, p = 0.26), sickness absence during the past year (median 5 vs. 3 days, p = 0.21), or unemployment or disability pension (5 vs. 4%, p = 0.62) did not significantly differ between AN probands and their unaffected peers. More women with AN were still studying (15 vs. 4%, p = 0.003), and half of them had children, as compared to 66% of unaffected women ( p = 0.05). Discussion The long-term prognosis of AN in the community appears promising. Weight-restoration is common and socio-demographic outcomes are generally favorable. However, women with a history of AN may be less likely to have children. © 2015 Wiley Periodicals, Inc. (Int J Eat Disord 2015; 48:851-859). [ABSTRACT FROM AUTHOR]

Background Both alcohol-specific genetic factors and genetic factors related to externalizing behavior influence problematic alcohol use. Little is known, however, about the etiologic role of these 2 components of genetic risk on alcohol-related behaviors across development. Prior studies conducted in a male cohort of twins suggest that externalizing genetic factors are important for predicting heavy alcohol use in adolescence, whereas alcohol-specific genetic factors increase in importance during the transition to adulthood. In this report, we studied twin brothers and sisters and brother-sister twin pairs to examine such developmental trajectories and investigate whether sex and cotwin sex effects modify these genetic influences. Methods We used prospective, longitudinal twin data collected between ages 12 and 22 within the population-based FinnTwin12 cohort study (analytic n = 1,864). Our dependent measures of alcohol use behaviors included alcohol initiation (age 12), intoxication frequency (ages 14 and 17), and alcohol dependence criteria (age 22). Each individual's genetic risk of alcohol use disorders ( AUD- GR) was indexed by his/her parents' and cotwin's DSM- IV Alcohol Dependence ( AD) criterion counts. Likewise, each individual's genetic risk of externalizing disorders ( EXT- GR) was indexed with a composite measure of parents' and cotwin's DSM- IV Conduct Disorder and Antisocial Personality Disorder criterion counts. Results EXT- GR was most strongly related to alcohol use behaviors during adolescence, while AUD- GR was most strongly related to alcohol problems in young adulthood. Further, sex of the twin and sex of the cotwin significantly moderated the associations between genetic risk and alcohol use behaviors across development: AUD- GR influenced early adolescent alcohol use behaviors in females more than in males, and EXT- GR influenced age 22 AD more in males than in females. In addition, the associations of AUD- GR and EXT- GR with intoxication frequency were greater among 14- and 17-year-old females with twin brothers. Conclusions We found divergent developmental trajectories for alcohol-specific and externalizing behavior-related genetic influences on alcohol use behaviors; in early adolescence, genetic influences on alcohol use behaviors are largely nonspecific, and later in adolescence and young adulthood, alcohol-specific genetic influences on alcohol use are more influential. Importantly, within these overall trajectories, several interesting sex differences emerged. We found that the relationship between genetic risk and problematic drinking across development is moderated by the individual's sex and his/her cotwin's sex. AUD- GR influenced adolescent alcohol outcomes in females more than in males and by age 22, EXT- GR influenced AD criteria more for males than females. In addition, the association between genetic risk and intoxication frequency was greater among 14- and 17-year-old females with male cotwins. [ABSTRACT FROM AUTHOR]

Background Adolescent alcohol abuse is associated with adverse outcomes in early adulthood, but differences in familial status and structure and household and community environments correlate with both adolescent drinking and adverse adult outcomes and may explain their association. We studied drinking-discordant twin pairs to evaluate such confounds to ask: Will between-family associations replicate in within-family comparisons? Methods With longitudinal data from >3,000 Finnish twins, we associated drinking problems at age 18½ with 13 outcomes assessed at age 25; included were sustained substance abuse, poor health, physical symptoms, early coital debut, multiple sexual partners, life dissatisfaction, truncated education, and financial problems. We assessed associations among twins as individuals with linear regression adjusted for correlated observations; within-family analyses of discordant twin pairs followed, comparing paired means for adult outcomes among co-twins discordant for adolescent problem drinking. Defining discordance by extreme scores on self-reported problem drinking at age 18½ permitted parallel analyses of twins as individuals and discordant twin pairs. Alternate definitions of pair-wise discordance and difference score correlations across the entire twin sample yielded supplementary analyses. Results All individual associations were highly significant for all definitions of discordance we employed. Depending on definitions of discordance, 11 to 13 comparisons of all drinking-discordant twin pairs and 3 to 6 comparisons of discordant monozygotic (MZ) twin pairs replicated between-family associations. For most outcomes, effect size attenuated from individual-level analysis to that within discordant MZ twin pairs providing evidence of partial confounding in associations reported in earlier research. The exception was the General Health Questionnaire (GHQ); at age 25, GHQ-12 had equivalent associations with age 18½ Rutgers Alcohol Problem Index across all comparisons. Conclusions Our analyses control for shared family background, and, partly or fully, for shared genes, to yield within-family replications and more compelling evidence than previously available that adolescent alcohol abuse disrupts transitions into early adulthood. [ABSTRACT FROM AUTHOR]

ABSTRACT Background To examine factors associated with the outcome of anorexia nervosa among women from the general population. Method Women ( N = 2,881) from the 1975-1979 birth cohorts of Finnish twins were screened for lifetime DSM-IV anorexia nervosa ( N = 55 cases) using questionnaires and the SCID interview. Potential factors associated with the likelihood of recovery were addressed in the same assessment. Recovery was defined as restoration of weight, menstruation, and the absence of bingeing and purging for at least one year prior to assessment. Using two-tailed t tests and Pearson's chi-square tests, we contrasted recovered ( N = 39) and unrecovered ( N = 16) women. We then used logistic regression adjusted for duration of illness and Cox proportional hazard models to account for the variable lengths of illness on prognostic factors. Results Unrecovered women were more likely to suffer from depressive symptoms prior to eating disorder onset (18.8% vs. 2.6%, p = 0.04), remain unemployed (18.8% vs. 2.6%, p = 0.04), report dissatisfaction with their current partner/spouse ( p = 0.02), and report high perfectionism ( p = 0.05) than were recovered women. When duration of illness was accounted for in the analyses, premorbid depression was the sole factor significantly associated with decreased likelihood of recovery (hazard ratio 0.17, 95% confidence interval: 0.03-0.89). Discussion Predicting the course of anorexia remains fraught with difficulty, but premorbid depressive symptoms are associated with poor outcome of anorexia nervosa in the general population. © 2013 Wiley Periodicals, Inc. (Int J Eat Disord 2014; 47:117-123) [ABSTRACT FROM AUTHOR]

Background Studies suggest that better cognitive and verbal abilities in childhood predict earlier experimentation with alcohol and higher levels of drinking in adolescence, whereas poorer ability is related to a higher likelihood of remaining abstinent. Whether individual differences in language development in childhood predict differences in adolescent drinking behaviors has not been studied. Methods To address that question, we compared co-twins from twin pairs discordant for their childhood language development and studied associations of parental reports of within-pair differences in age at speaking words, age at learning to read, and expressive language skills during school age with self-reported within-pair differences in drinking, intoxication, and alcohol-related problems across adolescence and young adulthood. Data from 2 longitudinal population-based samples of twin families were used, with verbal developmental differences in childhood reported by the parents when the twins were 12 and 16 years of age, respectively. Results Conditional logistic regression analyses and within-pair correlation analyses suggested positive associations between verbal development and drinking behaviors in both data sets. In analyses adjusted for birth order and birth weight, the co-twin reported to be verbally more advanced in childhood tended to report more frequent drinking and intoxication in adolescence in both samples. Better verbal development also was associated with the likelihood of having friends who drink in adolescence. Conclusions These findings suggest that, adjusting for familial and other factors shared by co-twins, better verbal development in childhood predicts more frequent drinking and intoxication in adolescence and young adulthood, possibly due, in part, to peer associations. [ABSTRACT FROM AUTHOR]

Objective To examine psychiatric comorbidity and factors that influence the outcome of bulimia nervosa (BN) in the general population. Method Women from the nationwide birth cohorts of Finnish twins were screened for lifetime BN ( N = 59) by using questionnaires and the Structured Clinical Interview for DSM-IV. We assessed psychiatric comorbidity and other prognostic factors. Results Among women with lifetime BN, the following were more common than among unaffected women: current major depressive disorder ( p = 0.004), lifetime major depressive disorder ( p = 0.00001) and heavy drinking ( p = 0.01). Decreased likelihood of recovery was associated with a history of lifetime major depressive disorder (hazard ratio (HR) 0.44, 95% confidence interval (CI) 0.23-0.84) and high drive for thinness at time of assessment (HR 0.96, 95% CI 0.93-0.99). Discussion Heavy drinking and depression present challenges for many women with BN. Major depressive disorder emerged as the only statistically significant prognostic factor of BN in this nationwide cohort; high drive for thinness was characteristic of the persistently ill. Copyright © 2012 John Wiley & Sons, Ltd and Eating Disorders Association. [ABSTRACT FROM AUTHOR]

Exercise is thought to increase the diameter of the conduit arteries supplying the muscles involved. We studied the effects of a physically active vs inactive lifestyle on artery diameters in monozygotic (MZ) twin pairs discordant over 30 years for leisure-time physical activity habits. In a population-based co-twin control study design, six middle-aged (50-65 years) same-sex MZ twin pairs with long-term discordance for physical activity were comprehensively identified from the Finnish Twin Cohort (TWINACTIVE study). Discordance was initially defined in 1975 and the same co-twin remained significantly more active during the 32-year follow-up. The main outcomes were arterial lumen diameters measured from maximal intensity projections of contrast-enhanced MR angiography images. Paired differences between active and inactive co-twins were studied. Compared with inactive members, active members of MZ twin pairs had larger diameters for the distal aorta and iliac and femoral arteries ( P<0.05 for all comparisons). The mean intrapair differences in the diameters of the arteries in these locations were 19% or larger. No significant differences between active and inactive co-twins ( P>0.2 for all comparisons) were found in the dimensions of the carotid arteries. Our genetically controlled study confirms that habitual physical activity during adulthood enlarges arteries in a site-specific manner. [ABSTRACT FROM AUTHOR]

Background: Twin studies demonstrate that measures of alcohol consumption (AC) show evidence of genetic influence, suggesting they may be useful in gene identification efforts. The extent to which these phenotypes will be informative in identifying susceptibility genes involved in alcohol dependence depends on the extent to which genetic influences are shared across measures of AC and alcohol problems. Previous studies have demonstrated that AC reported for the period of heaviest lifetime drinking shows a large degree of genetic overlap with alcohol dependence; however, many studies with genetic material assess current AC. Further, there are many different aspects of AC that can be assessed (e.g., frequency of use, quantity of use, and frequency of intoxication). Methods: Here, we use data from 2 large, independent, population-based twin samples, FinnTwin 16 and The Virginia Adult Twin Study of Psychiatric and Substance Use Disorders, to examine the extent to which genetic influences are shared across many different measures of AC and alcohol problems. Results: Genetic correlations across current AC measures and alcohol problems were high across both samples. However, both samples suggest a complex genetic architecture with many different genetic factors influencing various aspects of current AC and problems. Conclusions: These results suggest that careful attention must be paid to the phenotype in efforts to 'replicate' genetic effects across samples or combine samples for meta-analyses of genetic effects influencing susceptibility to alcohol-related outcomes. [ABSTRACT FROM AUTHOR]

Retrospective self-reports about prior sober and alcohol intoxicated states were explored to reveal moderating effects of trait anger and alcohol consumption on anger control. The analyses were based on self-reports of trait anger and alcohol consumption as well as self-reports of the participants’ typical levels of anger control in sober and alcohol intoxicated states in a population based sample of Finnish twins and their siblings (N = 4,852). The reported levels of anger control were lower regarding prior alcohol intoxicated states than sober states. A three-way interaction between alcohol consumption, trait anger and anger control was found. Whereas no interaction between alcohol consumption and trait anger was found in the self-reported sober state, there was an interactive effect of trait anger and alcohol consumption on anger control in the intoxicated state, indicating that the difference in anger control between those with high levels of alcohol consumption and those with low levels, was greater at higher levels of trait anger. Women had lower levels of anger control than men, but the relationship between trait anger, alcohol consumption and anger control was similar for both genders. In conclusion, the results showed that those with high levels of trait anger and alcohol consumption showed the lowest levels of anger control in self-reported alcohol intoxicated states, and indicate the importance of separating between anger control when sober and intoxicated since anger control seems to be differently related to at least trait anger and alcohol consumption in these states. [ABSTRACT FROM AUTHOR]

Long-term functional brain effects of adolescent alcohol abuse remain uncertain, partially because of difficulties in distinguishing inherited deficits from neuronal effects of ethanol and by confounds associated with alcohol abuse, especially nicotine exposure. We conducted a longitudinal twin study to determine neurocognitive effects of adolescent alcohol abuse, as measured with the auditory event-related potential (ERP) component P3, a putative marker of genetic vulnerability to alcoholism. Twin pairs ( N = 177; 150 selected for intrapair concordance/discordance for alcohol-related problems at age 18½) were recruited from ongoing studies of twins born 1975-1979 in Finland. Alcohol and tobacco use were assessed with questionnaires at ages 16, 17, 18½, and ∼25, and by a structured psychiatric interview concurrent with the ERP testing at mean age 25.8. During ERP recordings, subjects were instructed to detect target tones within a train of frequent 'standards' and to ignore occasional 'novel' sounds. To distinguish familial factors from ethanol effects, ERP and self-reported alcohol use measures were incorporated into hierarchical multiple regression (HMR) analysis, and intrapair differences in ERP were associated with intra-pair differences in alcohol variables. Novel-sound P3 amplitude correlated negatively with self-reported alcohol use in both between- and within-family analyses. No similar effect was observed for target-tone P3. HMR results suggest that twins' similarity for novel-sound P3 amplitude is modulated by their alcohol use, and this effect of alcohol use is influenced by genetic factors. Our results, from a large sample of twins selected from a population-based registry for pairwise concordance/discordance for alcohol problems at 18½, demonstrate that adolescent alcohol abuse is associated with subtle neurophysiological changes in attention and orienting. The changes are reflected in decreased novel-sound P3 amplitude and may be modified by genetic factors. [ABSTRACT FROM AUTHOR]

An association between childhood gender atypical behaviour (GAB) and a negative parent-child relationship has been demonstrated in several studies, yet the causal relationship of this association is not fully understood. In the present study, different models of causation between childhood GAB and parent-child relationships were tested. Direction of causation modelling was applied to twin data from a population-based sample (n = 2,565) of Finnish 33- to 43-year-old twins. Participants completed retrospective self-report questionnaires. Five different models of causation were then fitted to the data: GAB → parent-child relationship, parent-child relationship → GAB, reciprocal causation, a bivariate genetic model, and a model assuming no correlation. It was found that a model in which GAB and quality of mother-child, and father-child relationship reciprocally affect each other best fitted the data. The findings are discussed in light of how we should understand, including causality, the association between GAB and parent-child relationship. [ABSTRACT FROM AUTHOR]

The Rutgers Alcohol Problem Index (RAPI) is widely used to assess adolescent drinking-related problems. We asked how well RAPI, administered in late adolescence, predicts alcohol diagnoses at age 25 in a 7-year follow-up. At age 18, a population-based sample of Finnish twins completed RAPI by postal questionnaire; 597 (300 male) twins, from pairs discordant and concordant for age 18 RAPI scores, were interviewed at age 25 with the SSAGA, yielding DSM-IIIR diagnoses. Polychoric correlations between RAPI and alcohol diagnoses and symptoms, the area under the response operator characteristic (ROC) curve, and the odds ratio of outcome diagnosis per unit change in adolescent RAPI were analyzed. Twin pairs discordant for both adolescent RAPI and adult diagnoses permitted within-family replications for the full sample and separately by sex. Nearly half the interviewed twins met diagnostic criteria for alcohol dependency (46.2%) or abuse (1.5%). Age 18 RAPI scores significantly correlated with diagnoses (0.52) and symptom counts (0.55). ROC analysis found a 74% probability that adolescent RAPI scores will be higher among those with an alcohol diagnosis at age 25 than for those without. The odds ratio of outcome alcohol diagnosis per unit increase in adolescent 18 RAPI exceeded 10.0. Within-family comparisons of 117 twin pairs discordant for both age 18 RAPI and age 25 alcohol diagnoses replicated the between-family associations. In both between-family and within-family analyses, RAPI was more predictive of alcohol diagnoses among females. Our results offer evidence, including that from informative comparisons of co-twins discordant for both predictor and outcome, that RAPI scores in late adolescence robustly predict alcohol diagnoses in early adulthood. Accordingly, our results also provide new evidence that one pathway to problem drinking in early adulthood is a direct one from problem drinking in adolescence. [ABSTRACT FROM AUTHOR]

Background. Study of migrants offers a natural model to assess environmental risk of coronary heart disease (CHD) in countries differing in CHD occurrence. In Sweden, CHD risk has been markedly lower than in Finland from where a large migration occurred in the 1970s. Objectives. To study the structural and functional markers of subclinical atherosclerosis in twin pairs discordant for migration with the main focus on age at migration, length of residence and integration into Swedish society after migration from a high to a lower CHD risk country. Methods. Carotid intima-media thickness (IMT) and brachial artery endothelial function (EF) were assessed with high-resolution ultrasound and a set of cardiovascular, socio-economic and psychosocial risk factors were estimated in 76 middle-aged male twin pairs discordant for migration from Finland to Sweden. Results. Men who had migrated in adolescence had lower IMT values compared with their co-twins living in Finland (0.665 ± 0.114 vs. 0.802 ± 0.167 mm, P = 0.009). Also men who integrated well to Swedish society had lower (0.720 ± 0.154 vs. 0.799 ± 0.207 mm, P = 0.013) IMT values than their twin brothers living in Finland. Associations between IMT and migration age and between IMT and integration remained significant in multivariate analyses of several CHD risk factors. The intrapair difference in IMT was significantly associated with immigration age and integration (anova, P = 0.0082), the difference being greatest among pairs where the brother living in Sweden had migrated at early age and integrated well to Swedish society. EF was better in men who had migrated to Sweden before the age of 21 years, but not later, compared with their co-twins in Finland (6.4 ± 4.6% vs. 3.8 ± 3.6%, P = 0.025). Conclusions. Migration at an early age and good integration are beneficial to vascular health associated with moving from a high to a lower CHD risk country, suggesting that an environment-sensitive period influences atherogenesis before adulthood. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the changes in the multiple sclerosis (MS) concordance in twins, and the contribution of genetic and environmental factors to the aetiology of MS in Finland. Background: Both genes and the environment contribute to the development of MS. A well-conducted twin study is an excellent means to assess the relative contribution of heritability and environmental factors. Methods: Multiple sclerosis concordance was assessed for 10 Monozygotic and 14 dizygotic twin pairs using pairwise and probandwise concordance rates. The tetrachoric correlations in liability to disease for twin pairs were computed and a polygenic multifactorial model was used to estimate heritability. Results: The pairwise concordance for MZ twins was 30% and for the DZ twins 14.3%, compared with 30% for MZ and 0% for DZ 20 years ago. The corresponding probandwise concordance rates were 46.2% and 25%. The genetic variance (heritability) was 15.3% (95% Cl 0.0–77.6), the common environmental variance 73.7% (95% Cl 14.1–93.9) and the unique environmental variance 11.1% (95% Cl 2.3–30.0). Conclusions: As the concordance of MS in DZ twins has increased during the past two decades and the heritability estimate is low, it seems that the reported increase in MS incidence in Finland is mainly caused by environmental factors. [ABSTRACT FROM AUTHOR]

Summary 1. We studied how differences in the cost of producing male and female offspring in humans affected the productivity of twin vs. singleton deliveries in two ecologically different areas of pre-industrial (1752–1850) Finland. Given the higher energy requirements of male infants, we predicted sons to suffer more from increased litter size and food scarcity than daughters. 2. We found that the number of offspring surviving to adulthood from a twin delivery differed between the archipelago and mainland areas of rural Finland. On the mainland areas, where crop failures and subsequent famines were common throughout the centuries, twin deliveries were much less successful than in the south-west archipelago, where food conditions were traditionally more stable and survival was ensured by fishing. 3. Productivity of twin deliveries was modified by the gender composition of the twins; female–female twin births were generally most successful and male–male births least successful. 4. On the mainland, giving birth to twins of any gender composition never increased the mothers’ reproductive success beyond giving birth to either a male or female singleton, whereas in the archipelago mothers could increase their reproductive output by producing twins. This was because in the archipelago female–female twin deliveries contributed on average more than one adult offspring to the breeding population, whereas a singleton delivery of either gender produced only about 0·7 adults. 5. Our results show that increases in litter size and variability of food conditions increased male mortality. High female twin survival in the archipelago led to higher fitness of twinning mothers in relation to mothers with only singletons. Twinning has traditionally been significantly more common in the archipelago as compared to the mainland, but contrary to the prediction, there were no apparent differences in the frequency of male–male and... [ABSTRACT FROM AUTHOR]

Examines the etiological aspects on craniafacial morphology in twins with cleft lip and palate in Helsinki, Finland. Determination of craniofacial size by genetic factors; Correlation of increased differences between twins with increased severity of clefts; Influence of external factors on the craniofacial morphology of the twins.

The aims of this investigation were: 1) to study the effects of zygosity and the type of cleft on dental age in pairs of twins concordant or discordant for oral clefts, 2) to compare dental age in the twins with that in a population of normal Finnish children, and 3) to study asymmetry in the formation of mandibular teeth with regard to zygosity and the type of cleft. Twenty-two pairs of twins (8 mono- and 14 dizygotic) and one set of monozygotic triplets concordant or discordant for deft lip (CL), cleft palate (CP), or both (CLP) were investigated. Four of eight mono- and 12 of 14 dizygotic pairs were discordant for clefts. An orthopantomogram of both twins was taken on the same day. In 7 of the 8 monozygotic (88%) and in 4 of the l4 dizygotic (29%) pairs, the dental age was the same in both twins. Of the 12 pairs discordant for clefts, the dental age of the twin with cleft was delayed in 5, advanced in 3, and the same in 4 compared with that of the twin without a deft. The means of chronologic age and dental age were counted separately for the cleft subgroups and the non-cleft (NONC) group. The dental age was advanced in the CL twins and in the NONC twins, and was the same as chronologic age in the CP twins, but it was delayed in the CLP twins. Asymmetric formation of the 14 mandibular teeth (mostly the second premolars) was encountered in 3 of 8 CLP in 3 of 18 CP, in 1 of 16 NONC, and in none of 5 CL children. The great similarity in tooth formation among the monozygotic twins indicates strong genetic control of dental maturation in twins concordant and also discordant for cleft. [ABSTRACT FROM AUTHOR]

The relative roles of genetic and environmental factors in bruxism are not known. In 1990 a questionnaire sent to the Finnish Twin Cohort yielded responses from 1298 monozygotic and 2419 dizygotic twin pairs aged 33–60 years. We used structural equation modelling to estimate genetic and environmental components of variance in the liability to bruxism. There was a significant gender difference both in childhood (P =0.001) and adult (P =0.007) bruxism. Females compared to males reported childhood bruxism ‘often’ 5.2% vs 4.1% and ‘sometimes’ 17.4% vs 17.3%, and as adults ‘weekly’ 3.7% vs 3.8% and ‘monthly’ 3.9% vs 4.6%, respectively. Bruxism in childhood and adulthood is highly correlated (0.86 in males and 0.87 in females). The proportion of total phenotypic variance in liability to bruxism attributed to genetic influences in childhood bruxism was 49% (95% CI 37–60%) in males and 64% (55–71%) in females, and for adults 39% (27–50%) among males and 53% (44–62%) among females. The correlation between the genetic effects on childhood bruxism and the genetic effects on adult bruxism was estimated in a bivariate model to be 0.95 (95% CI 0.94–0.96) in males and 0.89 (0.88–0.90) in females. Bruxism appears to be quite a persistent trait. There are substantial genetic effects on bruxism both in childhood and as adults, which appear to be highly correlated. [ABSTRACT FROM AUTHOR]

To investigate the possible association of enterovirus (EV) infection with the development of multiple sclerosis (MS). The role of various genetic and environmental factors has been intensively studied in the etiopathogenesis of MS but the cause of the disease has remained unknown. Enteroviruses are possible candidates because they are neurotropic and able to cause chronic infections. Serum and cerebrospinal fluid (CSF) were tested with reverse transcription-polymerase chain reaction specific for enteroviruses in 17 MS twin pairs. No enteroviral RNA was found in any serum ( n = 34) or CSF ( n = 12) sample. We found no evidence of enterovirus infection in twins with MS or their healthy siblings. To our knowledge this is a first study to assess the role of enterovirus infections in the risk of developing MS in twins. [ABSTRACT FROM AUTHOR]