This fairly common mental illness used to be called manic depression or manic-depressive illness. The two poles indicated in the name refer to depression and mania. It is much more common than schizophrenia. Some patients with bipolar disorder experience psychotic symptoms such as hallucinations or delusions that may sometimes be mistaken for schizophrenia. However, the prominent mood symptoms, mania or depression, help distinguish it from schizophrenia.

Depression

When depressed, a patient with bipolar disease may lack energy and be sad, joyless, and uninterested in the world. She may not eat or sleep well. The depressive state can take a different form, with despair leading to tension, anxiety, restlessness, and fears that reach a delusional level.

Mania

When she is manic, a patient is overly, abnormally excited. She may also be irrationally enthusiastic, talkative, easily distracted, impatient, or irritated. Ideas speed through the mind. Concentration is poor. Constantly in motion, overly confident and sure of her ability to accomplish whatever pops into her mind, a patient in a manic state may spend money indiscriminately and make unrealistic plans.

Alternation in Mood

For some people, these extreme moods may alternate with one another in a cyclical fashion. In other cases, the patient may have symptoms that combine features of both depression and mania, or one may be dominant over the other. The different moods may come and go quickly or slowly.

Depression often dominates the disorder. For some, extreme manic states don't play a very large role, although patients may experience periods of elevated mood as they come out of a period of depression. Whichever mood dominates, some patients with the disorder may have psychotic symptoms, including delusions and hallucinations.