ADHD With Bipolar Disorder May Be Distinct Illness

Attention-deficit/hyperactivity disorder (ADHD) plus bipolar disorder is a distinct familial entity and perhaps even a distinct disorder, a study reported in the January Journal of Psychiatric Research suggests.

The study was headed by Joseph Biederman, M.D., a professor of psychiatry at Harvard Medical School.

Biederman and his colleagues studied 401 children with bipolar disorder, ADHD, or both, as well as nearly 1,200 of their relatives. They found that when children had bipolar disorder alone, their relatives were also more likely to have bipolar disorder alone; when children had ADHD alone, their relatives were also more likely to have ADHD alone, and when children had bipolar disorder in addition to ADHD, their relatives were also more likely to have both disorders.

“The co-segregation findings suggest that ADHD plus bipolar disorder is a distinct familial entity and, perhaps, a distinct disorder,” Biederman and his team said. “[And] the idea that ADHD comorbid with bipolar disorder is a distinct disorder is further supported by emerging neurobiological findings.” For example, the gene that codes for the dopamine transporter has been linked with both ADHD and bipolar disorder.

Further studies addressing genetic association and neuroimaging of subjects with both bipolar disorder and ADHD “may yield important information regarding course, treatment, and the neurobiology of bipolar disorder plus ADHD to determine if this combined condition should be considered a distinct disorder,” Biederman and his colleagues also noted.

The study was funded by the National Institutes of Health, the Heinz C. Prechter Bipolar Research Fund, the Massachusetts General Hospital Pediatric Psychopharmacology Council, and the Susan G. Berk Endowed Fund for Juvenile Bipolar Disorder. ■