The role of co-occurring conditions and genetics in the associations of eating disorders with attention-deficit/hyperactivity disorder and autism spectrum disorder.

Eating disorders (EDs) commonly co-occur with other psychiatric and neurodevelopmental disorders including attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD); however, the pattern of family history and genetic overlap among them requires clarification. This study investigated the diagnostic, familial, and genetic associations of EDs with ADHD and ASD. The nationwide population-based cohort study included all individuals born in Denmark, 1981-2008, linked to their siblings and cousins. Cox regression was used to estimate associations between EDs and ADHD or ASD, and mediation analysis was used to assess the effects of intermediate mood or anxiety disorders. Polygenic scores (PGSs) were used to investigate the genetic association between anorexia nervosa (AN) and ADHD or ASD. Significantly increased risk for any ED was observed following an ADHD [hazard ratio = 1.97, 95% confidence interval = 1.75-2.22] or ASD diagnosis [2.82, 2.48-3.19]. Mediation analysis suggested that intermediate mood or anxiety disorders could account for 44-100% of the association between ADHD or ASD and ED. Individuals with a full sibling or maternal halfsibling with ASD had increased risk of AN [1.54, 1.33-1.78; 1.45, 1.08-1.94] compared to those with siblings without ASD. A positive association was found between ASD-PGS and AN risk [1.06, 1.02-1.09]. In this study, positive phenotypic associations between EDs and ADHD or ASD, mediation by mood or anxiety disorder, and a genetic association between ASD-PGS and AN were observed. These findings could guide future research in the development of new treatments that can mitigate the development of EDs among individuals with ADHD or ASD.

Shared Genetic Factors Contributing to the Overlap between Attention-Deficit/Hyperactivity Disorder Symptoms and Overweight/Obesity in Swedish Adolescent Girls and Boys.

Attention-deficit/hyperactivity disorder (ADHD) and obesity are positively associated, with increasing evidence that they share genetic risk factors. Our aim was to examine whether these findings apply to both types of ADHD symptoms for female and male adolescents. We used data from 791 girl and 735 boy twins ages 16-17 years to examine sex-specific phenotypic correlations between the presence of ADHD symptoms and overweight/obese status. For correlations exceeding .20, we then fit bivariate twin models to estimate the genetic and environmental correlations between the presence of ADHD symptoms and overweight/obese status. ADHD symptoms and height/weight were parent- and self-reported, respectively. Phenotypic correlations were .30 (girls) and .08 (boys) for inattention and overweight/obese status and .23 (girls) and .14 (boys) for hyperactivity/impulsivity and overweight/obese status. In girls, both types of ADHD symptoms and overweight/obese status were highly heritable, with unique environmental effects comprising the remaining variance. Furthermore, shared genetic effects explained most of the phenotypic correlations in girls. Results suggest that the positive association of both types of ADHD symptoms with obesity may be stronger in girls than boys. Further, in girls, these associations may stem primarily from shared genetic factors.