Bipolar disorder

Bipolar disorder, formerly known as manic–depressive illness, is a chronic mental disorder characterized by recurrent episodes of elevated mood (mania or hypomania) and depression, with periods of relatively stable mood in between. These mood episodes can cause significant distress, impair social and occupational functioning, and increase the risk of suicide and other health problems. Bipolar disorder is a spectrum of conditions with varying severity and symptom patterns, and it requires long-term management through medication, psychotherapy, and lifestyle changes.

Classification and subtypes

Bipolar disorder is divided into several diagnostic subtypes based on the nature and severity of mood episodes. The two principal forms are bipolar I disorder and bipolar II disorder.

Bipolar I disorder is defined by the occurrence of at least one manic episode. Most individuals with bipolar I disorder also experience major depressive episodes, but a depressive episode is not required for the diagnosis. A manic episode is a period of abnormally and persistently elevated, expansive, or irritable mood and increased goal-directed activity or energy lasting at least one week, or requiring hospitalization. Psychotic features, such as delusions or hallucinations, may occur during severe mania or depression.

Bipolar II disorder is characterized by at least one hypomanic episode and at least one major depressive episode. Hypomania is a milder form of elevated mood that lasts at least four consecutive days and represents a clear change from the person’s usual functioning, but it is not severe enough to cause marked impairment, require hospitalization, or include psychosis. Despite the absence of full manic episodes, bipolar II disorder can be highly disabling because of recurrent depression.

Cyclothymic disorder is a chronic, fluctuating mood disturbance lasting at least two years in adults (one year in children and adolescents), involving numerous periods of hypomanic and depressive symptoms that do not meet full criteria for hypomanic or major depressive episodes. Other specified and unspecified bipolar and related disorders are used when symptoms cause significant distress or impairment but do not fully meet the criteria for the above categories.

The course of bipolar disorder can also be described using specifiers. A rapid-cycling pattern is defined as four or more mood episodes in a twelve-month period. Mixed features describe episodes in which symptoms of both mania and depression occur simultaneously, such as depressed mood combined with racing thoughts or increased energy. Other specifiers include anxious distress, psychotic features, catatonia, peripartum onset, and seasonal pattern.

Signs and symptoms

The symptoms of bipolar disorder depend on the type of mood episode. Mania, hypomania, and depression produce distinct changes in mood, energy, cognition, and behavior.

Mania and hypomania

A manic episode is characterized by a distinct period of abnormally and persistently elevated, expansive, or irritable mood, accompanied by increased energy or activity. To meet diagnostic criteria, at least three of the following symptoms must be present during the episode (four if the mood is predominantly irritable):

• Inflated self-esteem or grandiosity
• Decreased need for sleep, such as feeling rested after only a few hours
• Unusually talkative or pressured speech
• Flight of ideas or subjective experience that thoughts are racing
• Distractibility or difficulty maintaining attention
• Increase in goal-directed activity or psychomotor agitation
• Excessive involvement in pleasurable activities with a high potential for negative consequences, such as reckless spending, sexual indiscretions, or reckless driving

Mania may be severe enough to cause marked impairment in social or occupational functioning, require hospitalization, or include psychotic features. Hypomania involves the same symptom domains but is less severe, lasts at least four consecutive days, and does not cause marked impairment or require hospitalization. During hypomania, individuals may feel more productive, sociable, and creative, but the episode is noticeable to others and represents a change from baseline.

Depressive episodes

A major depressive episode in bipolar disorder is defined by at least two weeks of depressed mood or loss of interest or pleasure in nearly all activities, accompanied by at least four additional symptoms. These may include:

• Significant weight loss or gain, or changes in appetite
• Insomnia or hypersomnia
• Psychomotor agitation or retardation
• Fatigue or loss of energy
• Feelings of worthlessness or excessive guilt
• Difficulty concentrating or indecisiveness
• Recurrent thoughts of death, suicidal ideation, or suicide attempts

Bipolar depression can be difficult to distinguish from unipolar major depressive disorder. However, bipolar depression is more often associated with atypical features such as increased sleep, increased appetite, leaden paralysis, and a history of early age of onset. Depressive episodes in bipolar II disorder are often the predominant source of impairment.

Mixed features and other symptoms

Mixed features occur when a manic or hypomanic episode includes depressive symptoms, or when a depressive episode includes elevated mood or increased energy. These episodes are associated with higher distress, greater functional impairment, and increased risk of suicide. In addition to mood symptoms, many people with bipolar disorder experience cognitive difficulties, including problems with attention, memory, and executive function, both during mood episodes and sometimes between episodes. Anxiety disorders, substance use disorders, and attention-deficit/hyperactivity disorder frequently co-occur with bipolar disorder.

Causes and mechanisms

Bipolar disorder has a multifactorial etiology involving genetic, neurobiological, environmental, and psychosocial factors. No single cause has been identified.

Genetic factors

Family, twin, and adoption studies indicate a strong genetic contribution. The heritability of bipolar disorder is estimated to be approximately 60–80%, making it one of the most heritable psychiatric conditions. First-degree relatives of individuals with bipolar disorder have a significantly increased risk of developing the disorder or related mood conditions. Genome-wide association studies have identified many common genetic variants with small individual effects, as well as potential roles for genes involved in calcium signaling, circadian rhythms, and neuronal excitability. The genetic architecture is polygenic, meaning that many genes interacting with environmental factors contribute to risk.

Environmental factors

Stressful life events, childhood maltreatment, sleep disruption, and substance use, particularly cannabis and stimulants, are associated with the onset and recurrence of mood episodes. Childbirth and the postpartum period can trigger episodes in susceptible individuals. Circadian rhythm disruption, including shift work, jet lag, and irregular sleep patterns, is strongly linked to manic and depressive episodes. Environmental stressors do not cause bipolar disorder alone but can precipitate episodes in genetically vulnerable people.

Neurobiological mechanisms

Multiple neurotransmitter systems are implicated in bipolar disorder, including dopamine, serotonin, norepinephrine, glutamate, and gamma-aminobutyric acid. Dysregulation of the hypothalamic–pituitary–adrenal axis, inflammatory processes, mitochondrial dysfunction, and oxidative stress may also play roles. Neuroimaging studies have shown structural and functional differences in brain regions involved in emotion regulation, including the prefrontal cortex, amygdala, hippocampus, and striatum. Abnormalities in neural circuits that regulate reward, motivation, and impulse control are thought to contribute to manic and depressive symptoms.

Diagnosis

The diagnosis of bipolar disorder is based on clinical assessment, including a detailed psychiatric history, mental status examination, and information from family members or other observers when possible. There is no definitive laboratory test or biomarker. The diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), and the International Classification of Diseases, Eleventh Revision (ICD-11), require the presence of specific mood episodes as described above.

A careful history must distinguish bipolar disorder from unipolar depression, since a previous hypomanic or manic episode may be missed. Screening instruments such as the Mood Disorder Questionnaire, the Hypomania Checklist, and the Bipolar Spectrum Diagnostic Scale can help identify possible bipolar disorder, but they are not sufficient for diagnosis. Clinicians should also exclude medical and substance-related causes of mood symptoms, including thyroid disorders, neurological conditions, medications such as corticosteroids or stimulants, and substance intoxication or withdrawal.

Differential diagnoses include major depressive disorder, schizoaffective disorder, schizophrenia, borderline personality disorder, attention-deficit/hyperactivity disorder, and substance-induced mood disorder. The diagnosis of bipolar disorder in children and adolescents is more complex because irritability and mood lability are common in many childhood conditions. Clinicians generally look for discrete episodes of mood change with clear changes in energy and behavior, rather than chronic irritability alone.

Management

The treatment of bipolar disorder is multimodal and typically involves long-term pharmacotherapy, psychotherapy, and lifestyle interventions. Treatment is divided into acute management of manic, hypomanic, and depressive episodes, and maintenance treatment to prevent recurrence.

Pharmacotherapy

Mood stabilizers are the foundation of treatment. Lithium is one of the most effective medications for reducing both manic and depressive episodes and is associated with a reduction in suicide risk. It requires regular monitoring of serum levels, kidney function, and thyroid function. Anticonvulsant mood stabilizers include valproate, lamotrigine, and carbamazepine. Valproate is particularly effective for acute mania, while lamotrigine is used mainly for prevention of depressive episodes. Valproate should be avoided in women of childbearing potential when possible because of teratogenic risks.

Second-generation antipsychotics, including quetiapine, olanzapine, risperidone, aripiprazole, cariprazine, and lurasidone, are also effective in treating manic and mixed episodes. Several are approved for bipolar depression as well. Antidepressants are generally used with caution in bipolar disorder because they may precipitate mania, hypomania, or rapid cycling. If used, they are usually combined with a mood stabilizer or antipsychotic.

For bipolar depression, evidence supports the use of quetiapine, lurasidone, cariprazine, olanzapine–fluoxetine combination, and in some cases lamotrigine or lithium. Treatment-resistant mania or depression may require electroconvulsive therapy, which is highly effective for severe mood episodes, including during pregnancy. Emerging treatments include ketamine and esketamine for treatment-resistant bipolar depression, as well as transcranial magnetic stimulation.

Psychotherapy and psychosocial interventions

Psychotherapy is an important adjunct to medication. Evidence-based approaches include:

• Cognitive behavioral therapy focusing on identifying and modifying unhelpful thoughts and behaviors
• Interpersonal and social rhythm therapy, which emphasizes regularity of daily routines, sleep, and social rhythms
• Family-focused therapy, which improves communication and reduces expressed emotion
• Psychoeducation, which helps individuals and families understand the disorder, recognize early warning signs, and adhere to treatment

Lifestyle measures, including consistent sleep schedules, regular physical activity, avoidance of drugs and alcohol, and stress management, are important in preventing relapse. Support groups and peer support can also improve outcomes.

Prognosis

Bipolar disorder is often a recurrent and lifelong condition, but with appropriate treatment many people achieve substantial stabilization and functional recovery. The course varies widely. Some individuals have long periods of euthymia, while others experience frequent episodes or persistent subsyndromal symptoms. Even between episodes, cognitive and occupational difficulties may persist.

Suicide risk is markedly elevated in bipolar disorder. A significant proportion of people with the disorder attempt suicide at some point, and suicide rates are higher than in the general population. Factors associated with higher suicide risk include depressive and mixed episodes, rapid cycling, substance use, a history of suicide attempts, and comorbid anxiety or personality disorders. Early diagnosis, continuous treatment, and close monitoring reduce suicide risk.

Comorbid medical conditions, such as cardiovascular disease, diabetes, obesity, and thyroid disease, are common and contribute to reduced life expectancy. Life expectancy in people with bipolar disorder is estimated to be reduced by approximately 8–12 years compared with the general population, largely due to medical comorbidities and suicide.

Epidemiology

The lifetime prevalence of bipolar I disorder is approximately 1% of the general population, while the broader bipolar spectrum, including bipolar II and subthreshold forms, may affect 2–4% of people worldwide. The disorder occurs in both sexes, although bipolar II disorder and rapid cycling appear to be more common in women. The typical age of onset is late adolescence or early adulthood, with most cases beginning before age 25. Bipolar disorder is a leading cause of disability worldwide and is associated with high healthcare costs, lost productivity, and caregiver burden.

History

Descriptions of mania and melancholia date back to ancient Greek medicine. In the 19th century, French psychiatrists Jean-Pierre Falret and Jules Baillarger independently described circular and dual-form insanities, recognizing the alternating pattern of mania and depression. In the late 19th and early 20th centuries, German psychiatrist Emil Kraepelin consolidated recurrent mood disorders into a broad category he called “manic–depressive insanity,” distinguishing it from dementia praecox, now known as schizophrenia.

In the mid-20th century, the work of Karl Leonhard and others led to the distinction between bipolar and unipolar mood disorders. The Australian psychiatrist John Cade discovered the antimanic effects of lithium in 1949, and lithium became the first effective pharmacological treatment for bipolar disorder. The term “bipolar disorder” was adopted in the third edition of the DSM in 1980, replacing “manic–depressive illness” in official nomenclature.

Society and culture

Bipolar disorder is widely recognized in public discourse and media. Many public figures, artists, and writers have disclosed a diagnosis of bipolar disorder, which has helped raise awareness but has also contributed to romanticized or inaccurate portrayals. In reality, the disorder can be profoundly disabling and is associated with stigma, discrimination, and barriers to employment, housing, and healthcare.

Advocacy organizations such as the National Alliance on Mental Illness and the International Bipolar Foundation provide education, support, and policy advocacy. Legal issues may arise concerning involuntary psychiatric treatment, capacity to consent, and guardianship during severe mood episodes. Cultural factors influence how bipolar disorder is recognized, explained, and treated in different communities, and culturally sensitive care is an important component of effective management.

Research continues into the genetics, neurobiology, and treatment of bipolar disorder. New pharmacological agents, digital health tools, and personalized medicine approaches aim to improve early detection, reduce relapse, and enhance long-term outcomes for people living with the condition.