What Is Bipolar Disorder? Types, Symptoms, and Treatment

What Is Bipolar Disorder?

Bipolar disorder (formerly called manic-depressive illness) is a chronic psychiatric condition defined by abnormal and extreme shifts in mood, energy, activity level, and the ability to carry out day-to-day tasks. Unlike normal mood variation, the episodes in bipolar disorder are severe enough to disrupt relationships, work, and quality of life, and in some cases involve psychotic features or carry suicide risk. It affects approximately 1–4% of the global population across its various forms, with no significant gender difference in prevalence, though the illness manifests somewhat differently between men and women.

Bipolar disorder is not a single entity but a spectrum of related conditions. The key distinguishing feature among bipolar spectrum disorders is the presence and severity of elevated mood episodes (manic or hypomanic episodes), which differentiate bipolar disorder from unipolar depression. Genetic factors account for approximately 80% of the variance in bipolar disorder risk, making it one of the most heritable psychiatric conditions. First-degree relatives of a person with bipolar disorder have an 8–10 times higher risk of developing the condition compared with the general population.

Types of Bipolar Disorder

Bipolar I disorder is characterized by at least one lifetime manic episode lasting at least seven days (or less if hospitalization is required). Depressive episodes are common but not required for the diagnosis. Psychotic features—hallucinations or delusions—occur in approximately 50% of manic episodes in Bipolar I. Bipolar I carries the highest risk of hospitalization and is associated with significant morbidity and mortality.

Bipolar II disorder is defined by at least one hypomanic episode and at least one major depressive episode, but no full manic episodes. Hypomania is a milder form of elevated mood that is distinct in duration (at least four consecutive days) and does not cause marked functional impairment or require hospitalization, and is not accompanied by psychosis. Despite the milder elevated episodes, Bipolar II is not a milder form of the illness overall—patients spend the majority of their symptomatic time in depression, and the condition carries substantial impairment and suicide risk. Cyclothymic disorder involves chronic (at least two years) fluctuating periods of hypomanic symptoms and depressive symptoms that do not meet the full criteria for hypomanic or major depressive episodes.

Manic and Depressive Episodes

A manic episode is characterized by a distinct period of abnormally elevated, expansive, or irritable mood and increased energy or activity. During mania, patients commonly experience a drastically reduced need for sleep without feeling tired, grandiosity or inflated self-esteem, racing thoughts, flight of ideas, pressured speech, distractibility, and increased goal-directed activity. Critically, mania frequently drives impulsive, high-risk behaviors with potentially devastating consequences: reckless spending, sexual indiscretions, impulsive business decisions, substance use, and dangerous driving. When mania is accompanied by psychosis—believing one has special powers or a divine mission—the risk of harm escalates sharply.

Depressive episodes in bipolar disorder mirror major depressive disorder in their symptoms: persistent low or empty mood, anhedonia (loss of interest or pleasure in previously enjoyed activities), fatigue, worthlessness or guilt, cognitive impairment (poor concentration, indecisiveness), appetite and sleep changes, and suicidal ideation. Bipolar depression is distinct from unipolar depression in important ways: it tends to feature more hypersomnia (oversleeping), psychomotor retardation (slowed movement and thinking), and atypical features, and it carries a substantially higher risk of mixed features (simultaneous manic and depressive symptoms), which are associated with particularly high suicide risk.

Diagnostic Challenges

Bipolar disorder, particularly Bipolar II, is significantly underdiagnosed and misdiagnosed. The average delay from symptom onset to correct diagnosis is 9–12 years. Patients almost always present first seeking help for depression, and without direct questioning about past periods of elevated mood and energy, the bipolar diagnosis is missed. Misdiagnosis as unipolar depression is problematic because antidepressants used without a mood stabilizer can trigger manic episodes or induce rapid cycling (four or more mood episodes per year).

Other frequent misdiagnoses include ADHD (which shares the symptoms of distractibility, impulsivity, and restlessness), borderline personality disorder (which involves emotional dysregulation but typically lacks the episodic, sustained mood elevation of bipolar disorder), and schizophrenia (when psychotic features dominate). Comprehensive assessment involving a detailed longitudinal history, often supplemented by information from family members, is essential for accurate diagnosis.

Treatment: Mood Stabilizers and Beyond

Lithium is the gold-standard mood stabilizer and the only psychiatric medication with demonstrated antisuicidal effects. It prevents both manic and depressive recurrences and is particularly effective for classic euphoric mania. Lithium has a narrow therapeutic window—blood levels must be regularly monitored to avoid toxicity (which can cause tremor, polyuria, thyroid dysfunction, and in severe cases, neurotoxicity and renal impairment). Its mechanism involves multiple actions including inhibition of glycogen synthase kinase-3 (GSK-3β) and effects on second messenger systems.

Anticonvulsant mood stabilizers—valproate (valproic acid) and lamotrigine—are widely used alternatives or adjuncts. Valproate is particularly effective for mixed episodes and rapid cycling. Lamotrigine is superior to lithium in preventing depressive recurrences and is generally better tolerated, though it requires careful dose titration to avoid rare but serious skin reactions (Stevens-Johnson syndrome). Atypical antipsychotics (quetiapine, olanzapine, aripiprazole, lurasidone) are effective in acute mania and are increasingly used as maintenance treatments. Psychotherapy—particularly psychoeducation, interpersonal and social rhythm therapy (IPSRT), and CBT adapted for bipolar disorder—plays a vital role in helping patients recognize early warning signs, maintain regular sleep and social rhythms, and adhere to medication.