To Örebro University

ADHD may be associated with unhealthy dietary habits in children and adolescents. The link between diets and adult ADHD symptoms are not well established and the underlying genetic and environmental mechanisms remain unclear. Therefore, we firstly estimated associations between ADHD symptoms (inattention, hyperactivity or both) and three unhealthy dietary groups (unhealthy food, high-sugar food, and high-fat food), and also stratified based on age, sex, and socioeconomic status (SES). This was done using self-report data from a Swedish population-based twin study on ADHD symptoms and food frequency questionnaire in 17,999 twins, aged 20 to 47 years. Secondly, univariate and bivariate twin model-fitting anal-yses were conducted to determine the relative contribution of genetic and environmental factors to the observed associations. We have found that at the phenotypical level, ADHD total score were positively associated with unhealthy food (r = 0.11, 95% CI 0.09, 0.13), high-sugar food (r = 0.10, 95% CI 0.08, 0.12), and high-fat food (r = 0.11, 95% CI 0.09, 0.13). Similar association patterns were also found when analyzing separately the inattention and hyperactivity symptoms of the ADHD total score. All these associations remained stable across age, sex, and SES. Genetic and non-shared environmental effects accounted for similar proportions of the phenotypical correlations. The highest bivariate heritability was between ADHD total score and high-sugar food (h2 = 40%, 95% CI 7, 70). This study is the first to provide evidence for a genetic overlap between ADHD symptoms and unhealthy dietary habits. The remaining non-shared environmental effects also suggest an opportunity for treatments and interventions targets that focus on modifiable non-genetic risk factors.