To Örebro University

Many psychiatric disorders are associated with sex differences in prevalence. Recent studies indicate that females diagnosed with anxiety and depression carry more genetic risks related to attention deficit hyperactivity disorder (ADHD), compared to affected males. In this study, we tested whether females who have received clinical, register-based diagnoses of anxiety, depressive, bipolar, and eating disorders are at higher familial risk for ADHD and other neurodevelopmental disorders (NDs), compared to diagnosed males.

We analysed data from a record-linkage of several Swedish national registers, including 151,025 sibling pairs from 103,941 unique index individuals diagnosed with anxiety, depressive, bipolar, or eating disorders, as well as data from 646,948 cousin pairs. We compared the likelihood of having a relative diagnosed with ADHD and NDs in index males and females.

Females with anxiety disorders were more likely than affected males to have a brother diagnosed with ADHD [OR(CIs) = 1.13(1.05–1.22)]. Analyses of broader NDs suggested that ADHD diagnoses were driving this association. No further significant associations were found for ADHD in sisters or in individuals with depressive, bipolar, or eating disorders, or for ADHD in cousins. Follow-up analyses revealed similar point estimates for several categories of anxiety disorders, with the strongest effect observed for agoraphobia [OR(CIs) = 1.64(1.12–2.39)].

These results provide modest support for the possibility that familial/genetic risks for ADHD may show sex-specific phenotypic expression. Alternatively, there could be sex-specific biases in diag-noses of anxiety and ADHD. These factors could play a small role in the observed sex differences in prevalence of ADHD and anxiety.