We examined the association between having an ADHD diagnosis and risk of having a comorbid developmental phenotype using Swedish register data. We were interested in whether there is an interaction between sex and ADHD as it pertains to these comorbidities. Supplemental Table S9 displays the frequency of the disorder categories examined and the proportion of individuals affected overall and split by ADHD case status and sex. The male:female ratio for ADHD was 2:1. ADHD cases were at higher risk for all diagnostic categories, as compared with sex-matched controls (Table 1). Significant ADHD-by-sex interactions were observed for ASD and congenital malformations, suggesting that although in the context of ADHD both sexes are at increased risk for these comorbid problems, the increase in risk is even higher in female individuals compared with controls. A nominally significant association was observed for the interaction term for ID, which did not survive correction for multiple testing (Bonferroni correction for six independent tests: p-value threshold = .0083). Secondary analyses of severity of ID (where information was available) indicated that this weak association signal came from mild
