Bipolar disorder, also known as manic-depressive illness, is a brain disorder characterized by episodes of mania and depression. These episodes are
associated with unusual shifts in mood and energy.
Early onset bipolar disorder, which starts during
childhood or during the teen years, may be more
severe than forms that first appear in older teens and
adults. Some evidence suggests that young people
with the illness may have more frequent mood
switches, be sick more often, and have more mixed
episodes (both manic and depressive symptoms).