Research report that addresses what differences the age of onset of the disorder means in terms of severity of the illness. Early onset generally means that the illness is more severe overall, with greater familial risk.  Early onset indicates more psychosis, greater comorbidity with panic disorder and poorer response to lithium treatment.

by Joseph Biederman, Eric Mick, Stephen V. Faraone, Thomas Spencer, Timothy E. Wilens, and Janet Wozniak

Reproduced by permission of Elsevier Science from Biological Psychiatry, Vol. No. 48, pages 458-466, Copyright 2000 by the Society of Biological Psychiatry.

Despite ongoing controversy, the view that pediatric mania is rare or nonexistent has been increasingly challenged not only by case reports, but also by systematic research. This research strongly suggests that pediatric mania may not be rare but that it may be difficult to diagnose. Since children with mania are likely to become adults with bipolar disorder, the recognition and characterization of childhood-onset mania may help identify a meaningful developmental subtype of bipolar disorder worthy of further investigation.