Further evidence for co-segregation between pediatric obsessive compulsive disorder and attention deficit...

To examine the relationship between obsessive compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD) in children and adolescents using familial risk analysis.

We assessed for ADHD and OCD in the 1057 first-degree relatives of three groups of index children: those with OCD and ADHD, those with OCD but no ADHD and matched controls with neither disorder.

The age-corrected risk for OCD was similarly elevated in families of OCD youth with (14.8%) and without ADHD (17.5%) (p=.78), and both groups had significantly higher rates of OCD compared with controls (.5%) (p<.001). In contrast, the risk for ADHD was significantly elevated only among relatives of youth who had ADHD (15.3%) compared with controls (4.6%) (p<.001). Relatives affected with ADHD also had a significantly elevated risk for OCD compared to relatives unaffected by ADHD (20% vs. 4.9%, hazard ratio 4.8) (p<.001) and the two disorders occurred together with higher than expected frequency in affected relatives of OCD+ADHD probands (p<. 001) suggesting co-segregation between these two disorders. There was no evidence of nonrandom mating between OCD- and ADHD-affected spouses.

These results extend previous findings regarding the familiality of both OCD and ADHD and provide further evidence of a familial relationship between ADHD and pediatric OCD which best fit the hypothesis of a unique familial subtype.