BACKGROUND:

Family risk analysis can provide an improved understanding of the association between attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD), attending to the comorbidity with conduct disorder (CD).

METHODS:

We compared rates of psychiatric disorders in relatives of 78 control probands without ODD and CD (Control, N=265), relatives of 10 control probands with ODD and without CD (ODD, N=37), relatives of 19 ADHD probands without ODD and CD (ADHD, N=71), relatives of 38 ADHD probands with ODD and without CD (ADHD+ODD, N=130), and relatives of 50 ADHD probands with ODD and CD (ADHD+ODD+CD, N=170).

RESULTS:

Rates of ADHD were significantly higher in all three ADHD groups compared to the Control group, while rates of ODD were significantly higher in all three ODD groups compared to the Control group. Evidence for co-segregation was found in the ADHD+ODD group. Rates of mood disorders, anxiety disorders, and addictions in the relatives were significantly elevated only in the ADHD+ODD+CD group.

CONCLUSIONS:

ADHD and ODD are familial disorders, and ADHD plus ODD outside the context of CD may mark a familial subtype of ADHD. ODD and CD confer different familial risks, providing further support for the hypothesis that ODD and CD are separate disorders.