Background: To clarify the nosologic status of girls with attention deficit hyperactivity disorder (ADHD) who also satisfy diagnostic criteria for bipolar disorder (BPD).
Methods: Using blind raters and structured psychiatric interviews, we examined 140 girls with ADHD, 122 non-ADHD comparisons and their 786 first degree relatives. Analyses tested specific hypotheses about the familial relationship between ADHD and bipolar disorder in girls.
Results: After stratifying our ADHD sample into those with and without BPD, we 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 significantly differ in their relatives' risk for ADHD; (3) an elevated risk for bipolar disorder was observed among relatives when the proband child had BPD but not ADHD alone; (4) weak evidence of cosegregation between ADHD and BPD, and (5) no evidence of a trend for random mating between ADHD parents and those with mania.
Limitations: Limitations of this study include the lack of direct interviewing of probands and the limited number of ADHD/BPD probands available.
Conclusions: These findings extend to girls what was previously documented in boys and suggest that comorbid ADHD with BPD in girls is familially distinct from other forms of ADHD and may be related to what others have termed childhood onset BPD. Future work could determine if this subgroup has a characteristic course, outcome and response to treatment.