Answer:
Bipolar disorder is an episodic mood disorder, the hallmark of which are manic episodes - characterized by grandiosity, distractability, increased activity, excessive involvement in indiscreet activities, racing thoughts, pressured speech, and decreased need for sleep. These manic episodes are severe enough to cause impairment in social and occupational functioning, may be associated with psychotic features, and often result in hospitalization.
In addition to manic episodes, most individuals who suffer from bipolar disorder also experience periodic major depressive episodes. Although some residual symptoms may persist between episodes of mood disturbance, functioning is generally much improved during inter-episode periods. While medication can be quite helpful in reducing the frequency of episodes - and in reducing episode severity - many patients with bipolar disorder are resistant to staying on medication. Bipolar disorder affects approximately one of every 100 people, and appears to be equally distributed among men and women.
The diagnosis of bipolar disorder is made by clinical evaluation - including history and examination. Unfortunately, there appear to be no laboratory tests that are diagnostic. Although it is possible that brain imaging techniques may eventually be helpful in the clinical diagnosis of bipolar disorder, at present such techniques are not useful in a reliable way. Since bipolar disorder has a strong familial tendency, it is also possible that genetic techniques will eventually prove helpful in distinguishing bipolar disorder from other mood disorders or from other psychotic conditions. But, again, such approaches are not presently available. As a result, those who are concerned that they may suffer from bipolar disorder should seek a clinical evaluation by a psychiatrist.
With regard to the question of the development of bipolar disorder, the average age of onset is approximately 20. Although the pediatric precursors of - and possible pediatric manifestations of - this condition are a topic of active investigation, bipolar disorder is not generally discernible early in life.