Background: This study tested competing hypotheses about patterns of familial association between attention-deficit/hyperactivity disorder (ADHD) and anxiety disorders using familial risk analysis methodology.
Methods: The risk for ADHD and anxiety disorders in first-degree relatives was examined after stratifying ADHD probands by the presence or absence of comorbid anxiety disorders. The presence of anxiety disorders in probands and relatives was defined as meeting DSM-III-R diagnostic criteria for > or = 2 anxiety syndromes in the same subject.
Results: Familial risk analyses revealed that 1) the risk for anxiety disorders was significantly higher in ADHD probands and their relatives than in control probands and their relatives; 2) the risk for anxiety disorders among the relatives of ADHD probands was limited to those families in which the proband had a diagnosis of ADHD; 3) the risk for anxiety disorders was significantly higher among the relatives of ADHD probands with anxiety disorders than in relatives of ADHD probands without anxiety disorders, but these two groups did not differ in the familial risk for ADHD; and 4) ADHD and anxiety disorders did not cosegregate within families, and there was no evidence for nonrandom (assortative) mating.
Conclusions: These findings are most consistent with the hypothesis that ADHD and anxiety disorders segregate independently in families.