Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of depression and periods of abnormally elevated mood that last from days to weeks each. If the elevated mood is severe or associated with psychosis, it is called mania; if it is less severe, it is called hypomania. During mania, an individual behaves or feels abnormally energetic, happy, or irritable, and they often make impulsive decisions with little regard for the consequences. There is usually also a reduced need for sleep during manic phases. During periods of depression, the individual may experience crying and have a negative outlook on life and poor eye contact with others. The risk of suicide is high; over a period of 20 years, 6% of those with bipolar disorder died by suicide, while 30–40% engaged in self-harm. Other mental health issues, such as anxiety disorders and substance use disorders, are commonly associated with bipolar disorder.While the causes of bipolar disorder are not clearly understood, both genetic and environmental factors are thought to play a role. Many genes, each with small effects, may contribute to the development of the disorder. Genetic factors account for about 70–90% of the risk of developing bipolar disorder. Environmental risk factors include a history of childhood abuse and long-term stress. The condition is classified as bipolar I disorder if there has been at least one manic episode, with or without depressive episodes, and as bipolar II disorder if there has been at least one hypomanic episode (but no full manic episodes) and one major depressive episode. If the symptoms are due to drugs or medical problems, they are not diagnosed as bipolar disorder. Other conditions having overlapping symptoms with bipolar disorder include attention deficit hyperactivity disorder, personality disorders, schizophrenia, and substance use disorder as well as many other medical conditions. Medical testing is not required for a diagnosis, though blood tests or medical imaging can rule out other problems.Mood stabilizers—lithium and certain anticonvulsants such as valproate and carbamazepine—are the mainstay of long-term relapse prevention. Antipsychotics are given during acute manic episodes as well as in cases where mood stabilizers are poorly tolerated or ineffective or where compliance is poor. There is some evidence that psychotherapy improves the course of this disorder. The use of antidepressants in depressive episodes is controversial—they can be effective but have been implicated in triggering manic episodes. The treatment of depressive episodes is often difficult. Electroconvulsive therapy (ECT) is effective in acute manic and depressed episodes, especially with psychosis or catatonia. Admission to a psychiatric hospital may be required if a person is a risk to themselves or others; involuntary treatment is sometimes necessary if the affected person refuses treatment.Bipolar disorder occurs in approximately 1% of the global population. In the United States, about 3% are estimated to be affected at some point in their life; rates appear to be similar in females and males. The most common age at which symptoms begin is 20; an earlier onset in life is associated with a worse prognosis. Interest in functioning in the assessment of patients with bipolar disorder is growing, with an emphasis on specific domains such as work, education, social life, family, and cognition. Around a quarter to a third of people with bipolar disorder have financial, social, or work-related problems due to the illness. Bipolar disorder is among the top 20 causes of disability worldwide and leads to substantial costs for society. Due to lifestyle choices and the side effects of medications, the risk of death from natural causes such as coronary heart disease in people with bipolar disorder is twice that of the general population.