Medically reviewed by Dr. Alicia Moreno, PhD
Co-Occurring Disorders Editor & Mental Health · Last reviewed January 2025

Bipolar disorder is a chronic mood disorder characterized by episodes of mania or hypomania and episodes of depression. The NIMH estimates that 2.8% of U.S. adults — approximately 7 million people — have bipolar disorder, with nearly 83% of cases classified as severe. The disorder typically emerges in late adolescence or early adulthood, with a mean age of onset around 25 years.

Types of Bipolar Disorder

Bipolar I Disorder

Bipolar I is defined by the occurrence of at least one manic episode — a distinct period of abnormally elevated, expansive, or irritable mood lasting at least seven days, accompanied by increased activity/energy and at least three additional symptoms (grandiosity, decreased need for sleep, pressured speech, racing thoughts, distractibility, goal-directed activity, or risky behavior). Most people with Bipolar I also experience depressive episodes, though depression is not required for the diagnosis.

Manic episodes in Bipolar I are often severe enough to cause significant functional impairment, require hospitalization, or involve psychotic features.

Bipolar II Disorder

Bipolar II involves at least one hypomanic episode (a less severe form of mania lasting at least four days that does not cause significant functional impairment or require hospitalization) and at least one major depressive episode. Hypomanic episodes may feel positive — periods of elevated energy, creativity, and productivity. This often leads to underdiagnosis, as patients may not identify hypomanic episodes as problematic.

Bipolar II is predominantly a depressive illness — patients spend significantly more time in depressive episodes than hypomanic ones, and the depressive burden drives most impairment and suicide risk.

Bipolar Disorder and Substance Use

Bipolar disorder has one of the highest comorbidity rates with substance use disorders of any mental health condition. Studies suggest that approximately 45–60% of individuals with bipolar disorder have a lifetime co-occurring SUD. Substance use during manic episodes is particularly dangerous — it amplifies impulsivity and risky behavior and can trigger more severe mood episodes. Alcohol use is the most common co-occurring SUD. See our article on bipolar disorder and addiction.

Treatment

Mood Stabilizers

Mood stabilizers are the pharmacological foundation of bipolar disorder treatment. Lithium is the most extensively studied and remains the gold standard for Bipolar I — with evidence for both acute mania treatment and long-term relapse prevention, as well as a unique antisuicidal effect. Valproate and lamotrigine are widely used alternatives, with lamotrigine particularly effective for bipolar depression prevention.

Atypical Antipsychotics

Atypical antipsychotics (quetiapine, aripiprazole, lurasidone, and others) have FDA approval for various phases of bipolar disorder treatment, including acute mania, bipolar depression, and maintenance. Quetiapine is particularly commonly used for bipolar depression.

Psychotherapy

Psychotherapy for bipolar disorder is most effective in combination with pharmacotherapy. Evidence-based approaches include Interpersonal and Social Rhythm Therapy (IPSRT), which focuses on stabilizing daily routines and sleep-wake cycles; CBT adapted for bipolar disorder; and Family-Focused Therapy (FFT), which improves communication and reduces expressed emotion in families.