The exact cause of bipolar disorder is unknown, but several factors may be involved, such as:
- Biological differences. People with bipolar disorder appear to have physical changes in their brains. The significance of these changes is still uncertain but may eventually help pinpoint causes.
- Neurotransmitters. An imbalance in naturally occurring brain chemicals called neurotransmitters seems to play a significant role in bipolar disorder and other mood disorders.
- Inherited traits. Bipolar disorder is more common in people who have a first-degree relative, such as a sibling or parent, with the condition. Researchers are trying to find genes that may be involved in causing bipolar disorder.
There are several types of bipolar and related disorders. For each type, the exact symptoms of bipolar disorder can vary from person to person. Bipolar I and bipolar II disorders also have additional specific features that can be added to the diagnosis based on your particular signs and symptoms.
Criteria for bipolar disorder
The Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published by the American Psychiatric Association, lists criteria for diagnosing bipolar and related disorders. This manual is used by mental health providers to diagnose mental conditions and by insurance companies to reimburse for treatment.
Diagnostic criteria for bipolar and related disorders are based on the specific type of disorder:
- Bipolar I disorder. You’ve had at least one manic episode. The manic episode may be preceded by or followed by hypomanic or major depressive episodes. Mania symptoms cause significant impairment in your life and may require hospitalization or trigger a break from reality (psychosis).
- Bipolar II disorder. You’ve had at least one major depressive episode lasting at least two weeks and at least one hypomanic episode lasting at least four days, but you’ve never had a manic episode. Major depressive episodes or the unpredictable changes in mood and behavior can cause distress or difficulty in areas of your life.
- Cyclothymic disorder. You’ve had at least two years — or one year in children and teenagers — of numerous periods of hypomania symptoms (less severe than a hypomanic episode) and periods of depressive symptoms (less severe than a major depressive episode). During that time, symptoms occur at least half the time and never go away for more than two months. Symptoms cause significant distress in important areas of your life.