His work in the early 20th century led to advancements in classifying, treating, and predicting the course of mental illness, which ushered in the formal discipline of psychiatry. An onset before the age of 30 usually results in frequent, severe episodes. Psychosis is more common in this group and symptoms tend to linger between episodes. An onset after the age of 40 has a better prognosis. Generally, short episodes, late onset, the absence of other medical or psychiatric conditions, and early treatment have a better prognosis.
Most people are symptom free for months or even years between episodes of depression and mania.
Three-fourths of manic episodes occur before or right after a major depressive episode. Typically, a greater number of manic episodes are experienced over a lifetime. During hypomanic episodes, patients may become more productive or noticeably goal driven, but their ability to function well in their normal daily activities is not impaired. The age of onset is usually the late teens or early 20s and there is usually a history of depression. Men and women are affected in equal numbers.