Bipolar disorder is an affective disorder characterized by severe fluctuations in mood, involving episodes of mania, hypomania, and major depression, with oscillating remission and recurrence. Approximately half of patients will have a predominance of either depressive or manic episodes. There are 2 subtypes:

• Bipolar type 1 – Patients experience manic episodes and, in most cases, also experience major depressive and hypomanic episodes.
• Bipolar type 2 – Patients experience at least 1 hypomanic episode and at least 1 major depressive episode but do not have manic episodes.

Mania is a major criterion for bipolar type 1. Hypomania, a major criterion for bipolar type 2, consists of some of the same characteristics but generally does not result in the same functional impairment. Mania is often characterized by an expansive euphoria, inflated self-esteem, grandiosity, disinhibition, and increased irritability. Many patients engage in riskier behaviors during manic episodes, including substance use, spending excessive money, etc. Other signs of mania include pressured speech, racing thoughts, flight of ideas, distractibility, psychomotor agitation, restlessness, hypersexuality, and insomnia or sleep disturbance. Mania may also present with psychotic symptoms.

The estimated prevalence of bipolar type 1 and bipolar type 2 disorders in the United States is 1.8%. The bipolar disorders have the highest genetic link of all major mental illnesses, with an up to tenfold increase in risk among individuals with relatives who have bipolar disorders. Symptoms usually begin in early adulthood, and bipolar disorder is less commonly diagnosed during childhood or adolescence. There is no difference between the sexes in prevalence of the disease. However, women are more likely to experience more depressive symptoms than men.

Coexisting psychiatric conditions are often present and are associated with a worse prognosis. Common comorbidities include anxiety, substance use disorder, eating disorders, borderline and other personality disorders, and attention deficit hyperactivity disorder. 

Other chronic medical conditions more prevalent in this patient population are metabolic syndrome, migraine, obesity, and type 2 diabetes mellitus.

There is an increased risk of substance use disorders and suicidal ideation or suicide attempt in individuals with bipolar disorder. Patients with coexisting psychiatric conditions, especially anxiety disorder, are at higher risk for suicide attempt or death by suicide. Other factors that increase suicide risk include older age, predominant depression, a first-degree relative with a mood disorder or who committed suicide, sexual dysfunction, and bipolar episodes that are more frequent or severe. Women are more likely to attempt suicide; men are more likely to die by suicide.

Patients with this disorder may have an increased risk of various general medical conditions.