Definition:

Bipolar disorder, previously known as manic depressive illness, is a severe chronic mood disorder, characterized by the recurrence of mania (hypomania), depression, or mixed episodes. It is one of the main causes of disability among young people, leading to cognitive and functional impairment and raised mortality, particularly death by suicide. Mania is the most characteristic phase of bipolar disorder. While mood elevation and euphoria are commonly described phenotypic descriptors of mania, irritability and anger may dominate. At the present time, there is solid evidence supporting the use of lithium, the anticonvulsants valproate and carbamazepine, and some antipsychotics in mania. Manic or hypomanic episodes differ in severity and length. In a hypomanic episode, a disturbance in functioning can be seen by others but does not typically cause severe impairment or require admission to hospital. At onset, most patients with bipolar disorder present with a depressive episode that differs subtly from unipolar depression. The first step in the management of bipolar disorder is to confirm the diagnosis of mania or hypomania and define the patient's mood state, because the therapeutic approach differs considerably for hypomania, mania, depression, and euthymia. While effective pharmacological treatments exist for bipolar disorder, the pathophysiology of the condition essentially remains unknown. Although bipolar disorder is one of the most heritable psychiatric disorders, a multifactorial model in which gene and environment interact is currently thought to best fit this disorder. Many risk alleles of small effect which are described in genome-wide association studies, contribute to the polygenic risk of bipolar disorder. It is suggested that the dopaminergic system may play a central role in bipolar disorder, although no singular dysfunction of neurotransmitter systems has been identified.