Sex and age genetic overlap between body mass index and attention deficit hyperactivity disorder in twins

Abstract

Aim: To examine the genetic and environmental contributions to the association between attention-deficit/hyperactivity disorder (ADHD) symptoms and body mass index (BMI) among children and adolescents, and to assess variation by sex and developmental stage in a non-Western population using a twin design.

Methods: A total of 1,774 same-sex twins aged 6-18 years (1,150 monozygotic and 624 dizygotic) were drawn from the Chinese Child and Adolescent Twin Registry. ADHD symptoms were assessed using the parent-reported Child Behavior Checklist. Univariate and bivariate Cholesky decomposition models were applied to estimate additive genetic, shared environmental, and unique environmental contributions to ADHD symptoms and BMI, as well as their covariance, with analysis stratified by sex and age group (children aged 6-11 years and adolescents aged 12-18 years).

Results: Genetic factors accounted for 46% of the variance in ADHD symptoms and 88% of the variance in BMI. A significant positive phenotypic association was observed between ADHD symptoms and BMI (β = 0.29, P < 0.01), particularly among girls and adolescents. Bivariate twin modeling indicated a modest genetic correlation between ADHD symptoms and BMI in the full sample (r_g = 0.13), with higher and statistically significant genetic correlations observed in girls (r_g = 0.23) and in children (r_g = 0.17). In adolescents, both genetic and unique environmental factors contributed to the association, with relatively greater unique environmental contributions in boys.

Conclusion: These findings indicate etiologically heterogeneous pathways linking ADHD symptoms and BMI across childhood and adolescence by sex and developmental stage, supporting neurobehaviorally informed risk stratification and prevention strategies.

Keywords

ADHD symptoms / childhood obesity / twin study / genetic overlap / sex differences

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