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Background: Restrictive eating problems are rare in children but overrepresented in those with neurodevelopmental problems. Comorbidities decrease wellbeing in affected individuals but research in the area is relatively scarce. This study describes phenotypes, regarding psychiatric and gastrointestinal comorbidities, in children with restrictive eating problems. Methods: A parental telephone interview was conducted in 9- or 12-year old twins ( n = 19,130) in the Child and Adolescent Twin Study in Sweden. Cases of restrictive eating problems and comorbid problems were established using the Autism, Tics-AD/HD and other Comorbidities inventory, parental reports of comorbidity as well as data from a national patient register. In restrictive eating problem cases, presence of psychiatric and gastrointestinal comorbidity was mapped individually in probands and their co-twin. Two-tailed Mann-Whitney U tests were used to test differences in the mean number of coexisting disorders between boys and girls. Odds ratios were used to compare prevalence figures between individuals with or without restrictive eating problems, and Fisher exact test was used to establish significance. Results: Prevalence of restrictive eating problems was 0.6% (concordant in 15% monozygotic and 3% of dizygotic twins). The presence of restrictive eating problems drastically increased odds of all psychiatric problems, especially autism spectrum disorder in both sexes (odds ratio = 11.9 in boys, odds ratio = 10.1 in girls), obsessive-compulsive disorder in boys (odds ratio = 11.6) and oppositional defiant disorder in girls (odds ratio = 9.22). Comorbid gastrointestinal problems, such as lactose intolerance (odds ratio = 4.43) and constipation (odds ratio = 2.91), were the most frequent in girls. Boy co-twins to a proband with restrictive eating problems generally had more psychiatric problems than girl co-twins and more girl co-twins had neither somatic nor any psychiatric problems at all. Conclusions: In children with restrictive eating problems odds of all coexisting psychiatric problems and gastrointestinal problems are significantly increased. The study shows the importance of considering comorbidities in clinical assessment of children with restrictive eating problems. [ABSTRACT FROM AUTHOR]

Background: The normal development of cortisol regulation during childhood is thought to be influenced by a complex interplay between environmental and genetic factors.Method: The aim of this study was to estimate genetic and environmental influences on basal cortisol levels in a sample of 151 twin pairs aged 9-16 years. Salivary cortisol was collected on two consecutive days when the children attended school--immediately after awakening, 30 min post-awakening and at bedtime.Results: Heritability was highest (60%) for cortisol levels about 30 min after awakening. For samples taken immediately at awakening heritability was less pronounced (28%) and in the evening low (8%).Conclusion: The limited genetic influence on evening levels, moderate on cortisol at awakening and high on awakening response, might imply two genetic regulation patterns, one specifically for awakening response and one for the circadian rhythm proper. These findings could explain divergent results in previous studies and highlight the importance of taking the circadian rhythm into account in studies of cortisol levels in children. [ABSTRACT FROM AUTHOR]

Background Although neurodevelopmental disorders are demarcated as discrete entities in the Diagnostic Statistical Manual of mental disorders, empirical evidence indicates that there is a high degree of overlap among them. The first aim of this investigation was to explore if a single general factor could account for the large degree of observed overlap among neurodevelopmental problems, and explore whether this potential factor was primarily genetic or environmental in origin. The second aim was to explore whether there was systematic covariation, either genetic or environmental, over and above that contributed by the potential general factor, unique to each syndrome. Method Parents of all Swedish 9- and 12-year-old twin pairs born between 1992 and 2002 were targeted for interview regarding problems typical of autism spectrum disorders, ADHD and other neurodevelopmental conditions (response rate: 80 percent). Structural equation modeling was conducted on 6,595 pairs to examine the genetic and environmental structure of 53 neurodevelopmental problems. Results One general genetic factor accounted for a large proportion of the phenotypic covariation among the 53 symptoms. Three specific genetic subfactors identified 'impulsivity,' 'learning problems,' and 'tics and autism,' respectively. Three unique environment factors identified 'autism,' 'hyperactivity and impulsivity,' and 'inattention and learning problems,' respectively. Conclusion One general genetic factor was responsible for the wide-spread phenotypic overlap among all neurodevelopmental symptoms, highlighting the importance of addressing broad patient needs rather than specific diagnoses. The unique genetic factors may help guide diagnostic nomenclature, whereas the unique environmental factors may highlight that neurodevelopmental symptoms are responsive to change at the individual level and may provide clues into different mechanisms and treatments. Future research would benefit from assessing the general factor separately from specific factors to better understand observed overlap among neurodevelopmental problems. [ABSTRACT FROM AUTHOR]

Objective: Attention-deficit/hyperactivity disorder (ADHD) is more frequent in males than in females. The "female protective effect" posits that females undergo greater exposure to etiological factors than males in order to develop ADHD, leading to the prediction that relatives of females with ADHD will display more ADHD behaviors. We thus tested whether cotwins of females displaying extreme ADHD traits would display more ADHD traits than cotwins of males displaying extreme ADHD traits.Method: Parents of approximately 7,000 pairs of nonidentical twins in Sweden, and approximately 4,000 pairs of twins in England and Wales, completed dimensional assessments of ADHD traits. Probands were selected on the basis of scoring within the highest 10% of the distribution in each sample. Dimensional scores of cotwins of probands, as well as the categorical recurrence rate, were investigated by proband sex.Results: Cotwins of female probands displayed higher mean ADHD trait scores (mean = 0.62-0.79) than cotwins of male probands (mean = 0.38-0.55) in both samples. This trend was significant in the Swedish sample (p < .01) and when the 2 samples were merged into a single, larger sample (p < .001). When the samples were merged, there was also a significant association between proband sex and cotwin's categorical status, with more cotwins of female probands also being probands than cotwins of male probands.Conclusion: These findings support a female protective effect against ADHD behaviors, suggesting that females require greater exposure to genetic and environmental factors associated with ADHD in order to develop the condition. [ABSTRACT FROM AUTHOR]