Objective: To clarify the nosological status of children with attention-deficit hyperactivity disorder (ADHD) who also satisfy diagnostic criteria for bipolar disorder (BPD).
Method: Blind raters and structured psychiatric interviews were used to examine 140 children with ADHD, a sample of 120 non-ADHD comparisons, and their 822 first-degree relatives. Data analyses tested specific hypotheses about the familial relationship between ADHD and BPD.
Results: After stratifying the ADHD sample into those with and without BPD, the authors found that (1) relatives of both ADHD subgroups were at significantly greater risk for ADHD than relatives of non-ADHD controls; (2) the two subgroups did not differ significantly from one another in their relatives' risk for ADHD; (3) a fivefold elevated risk for BPD was observed among relatives when the proband child had BPD but not when the proband had ADHD alone; (4) an elevated risk for major depression with severe impairment was found for relatives of ADHD + BPD probands; (5) both ADHD and BPD occurred in the same relatives more often than expected by chance alone; and (6) there was a trend for random mating between ADHD parents and those with mania.
Conclusions: The data suggest that comorbid ADHD with BPD is familially distinct from other forms of ADHD and may be related to what others have termed childhood-onset BPD.