Family studies indicate that if one parent has a mood disorder, their child will have a risk of between 10 and 25 percent for a mood disorder. If both parents are affected, the risk roughly doubles. The risk increases if more members of the family are affected, especially first-degree relatives rather than more distant relatives. Studies of twins provide evidence that genes account for 50 to 70 percent of mood disorders, leaving environmental or nonheritable factors to account for the remainder.

How does Bipolar I Disorder typically develop?

Bipolar I disorder most often starts with depression. Most individuals experience both depressive and manic episodes; however, 10 to 20 percent experience only manic episodes.

Manic episodes typically have a rapid onset of hours or days, but they may evolve over a few weeks. An untreated manic episode lasts about 3 months. Of people who have a single manic episode, 90 percent are likely to have another. As the disorder progresses, the time between episodes often decreases. After about five episodes, however, the time between manic episodes often stabilizes at 6 to 9 months.

Of persons with bipolar disorder, 5 to 15 percent have four or more episodes per year and can be classified as rapid cyclers.

Does Bipolar Disorder affect men differently than women?

Yes. In contrast to major depressive disorder, which affects women twice as much as men, manic episodes are more common in men. When manic episodes occur in women, they are more likely than men to present a mixed picture, such as mania combined with depression. Women also have a higher rate of being rapid cyclers, defined as having four or more manic episodes in a 1-year period.

What is Bipolar II Disorder?

A person with bipolar II disorder experiences periods of both hypomania and major depression but never has had a manic episode.

Hypomanic Episodes

A hypomanic episode has all the symptoms of a manic episode that characterizes bipolar 1 disorder, with two distinct differences:

• A hypomanic episode lasts for at least 4 consecutive days (instead of 7 in a manic episode).
• A hypomanic episode is associated with an uncharacteristic change in behavior but is not severe enough to cause marked impairment in social or occupational functioning or to require hospitalization (as a manic episode may cause).

Major Depression

Symptoms of major depression include five or more symptoms during the same 2-week period: a depressed mood for most of the day, nearly every day, a loss of interest in pleasure and activities, significant weight loss or weight gain, insomnia or sleeping too much, fatigue, feelings of worthlessness or excessive guilt, diminished ability to think or concentrate, or recurrent thoughts of death or suicide. The symptoms cause significant distress or impairment in social, occupation, or other important areas of functioning.

For a bipolar II diagnosis, neither the hypomanic episodes nor major depressive episodes can be attributable to the physiological effects of a substance (e.g., drug of abuse or medication) or other medical condition.

What is Cyclothymic Disorder?

Cyclothymic disorder is a type of bipolar condition that is diagnosed when a person experiences during a 2-year period (1 year for children):

• Numerous periods with hypomanic symptoms that do not meet the full criteria for a hypomanic episode and numerous periods of depressive symptoms that do not meet the full criteria for a major depressive episode.
• The hypomanic and depressive symptoms have been present for at least half the time, and the individual has been without the symptoms for no more than 2 months at a time.
• The symptoms cause significant distress or impairment in social, occupational, or other important areas of functioning.
• The symptoms are not attributable to the physiological effects of a substance (e.g., drug of abuse or medication) or another medical condition (e.g., hyperthyroidism or schizophrenia).

What is Substance/Medication-Induced Bipolar Disorder?

Substance/medication-induced bipolar disorder is a type of bipolar condition that is caused by substance intoxication or withdrawal or exposure to a medication.

The disorder is characterized by an elevated, expansive or irritable mood or a markedly diminished interest or pleasure in all, or almost all, activities. It may also be accompanied by a depressed mood. The symptoms occur during or soon after substance intoxication or withdrawal or following exposure to a medication.

The symptoms cause significant distress or impairment in social, occupation, or other important areas of functioning.