What Is Bipolar Disorder? Types, Symptoms, Causes, and Treatment Options

Bipolar disorder is a chronic psychiatric condition characterized by recurring mood episodes that alternate between mania or hypomania — states of abnormally elevated or irritable mood and increased energy — and depression. The shifts in mood, cognition, energy, and behavior that define bipolar disorder are qualitatively different from everyday emotional ups and downs: they last days to weeks, are severe enough to impair work and relationships, and in the case of full mania include psychosis (losing contact with reality).

Bipolar disorder affects approximately 2.8% of U.S. adults in any given year, with 82.9% of those cases classified as severe (National Institute of Mental Health [NIMH], 2024). Globally, bipolar spectrum disorders, encompassing Bipolar I, Bipolar II, and cyclothymia, affect more than 1% of the world’s population, contribute to disability and premature mortality, and are associated with elevated risk of cardiovascular disease and suicide compared to the general population (Oliva et al., 2024).

KEY HIGHLIGHTS

• Bipolar disorder is not just mood swings: It is a diagnosable psychiatric condition with defined episode types, specific DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) criteria for each, and measurable neurobiological differences in brain structure and chemistry. Mood episodes in bipolar disorder last days to months — not hours — and represent a distinct change from the person’s baseline functioning (American Psychiatric Association, 2022).
• 2.8% of U.S. adults affected annually: NIMH data confirms that 2.8% of U.S. adults met criteria for bipolar disorder in the past year, with nearly 83% classified as severe. Bipolar disorder has no noteworthy gender difference in overall prevalence, unlike most other mood disorders (NIMH, 2024).
• Diagnosis is frequently delayed or missed: Because people with bipolar disorder most seek help during depressive episodes — not manic ones — they are initially diagnosed with unipolar depression. Antidepressant monotherapy (a single antidepressant prescribed without a mood stabilizer) triggers or accelerates manic episodes in people with undiagnosed bipolar disorder, making accurate initial diagnosis clinically critical (Oliva et al., 2024; NIMH, 2024).
• Neurobiology is measurable: Bipolar disorder involves structural and functional brain differences, including reduced prefrontal cortex gray matter volume, amygdala dysfunction, and disrupted circadian (daily biological rhythm) regulation. These neurobiological differences are not moral or character failings — they reflect a medical condition with identifiable biological substrates (Oliva et al., 2024).
• Heritability is 60–85%: Bipolar disorder is among the most heritable psychiatric conditions. First-degree relatives of someone with bipolar disorder face an approximately 10-fold increased risk compared to the general population. However, genetics alone do not determine outcome — environmental stressors, sleep disruption, and substance use are key modifiable risk factors (NIMH, 2024; Oliva et al., 2024).
• Treatment is effective and lifelong: Bipolar disorder is a lifelong condition with no cure, but it is highly manageable with the right combination of medication and psychotherapy. Mood stabilizers — particularly lithium — remain the cornerstone of long-term treatment and have strong evidence for reducing both mania relapse and suicide risk (Oliva et al., 2024).
• A 2025 meta-analysis updated Bipolar II treatment evidence: A systematic review and meta-analysis published in August 2025 in the Journal of Affective Disorders, covering 10 randomized trials and 645 adults with Bipolar II, assessed the relative efficacy of lithium and lamotrigine, underscoring the importance of disorder-specific pharmacological guidance rather than generic mood stabilizer prescribing (Fredskild et al., 2025).

What Is Bipolar Disorder?

Bipolar disorder is a chronic mood disorder defined by the recurrence of distinct mood episodes — mania, hypomania, and major depressive episodes — that represent a clear change from a person’s usual behavior and that are severe enough to cause major functional impairment. The term “bipolar” refers to the two poles of mood the disorder involves: elevated (manic or hypomanic) and depressed.

Not every person with bipolar disorder experiences all episode types equally. In Bipolar I disorder, the defining feature is at least one full manic episode, and while most people also experience major depressive episodes, depression is not required for a Bipolar I diagnosis. In Bipolar II disorder, by contrast, full mania has never occurred; instead, there is a pattern of hypomanic episodes and major depressive episodes, with the depressive burden being the more clinically prominent problem (American Psychiatric Association, 2022).

Bipolar disorder was formerly called manic-depressive illness or manic depression, terms that have largely been replaced in clinical and public communication because they carried substantial stigma and were applied imprecisely across a wide array of mood presentations. The more specific modern terminology, which distinguishes between types, episode polarity, and severity, allows for more accurate diagnosis and treatment planning.

What Are the Types of Bipolar Disorder?

The types of bipolar disorder recognized in the DSM-5 are Bipolar I disorder, Bipolar II disorder, cyclothymic disorder, and other specified or unspecified bipolar and related disorders. Each type is defined by a distinct pattern of episode types, durations, and functional impact. The comparison below highlights the key clinical distinctions:

Feature	Bipolar I	Bipolar II	Cyclothymia
Defining episode	At least one full manic episode lasting ≥7 days (or requiring hospitalization)	At least one hypomanic episode (≥4 days) AND at least one major depressive episode; no full mania	Numerous periods of hypomanic AND depressive symptoms over ≥2 years; not meeting full criteria for either
Mania severity	Full mania: severe, with psychosis; requires hospitalization; significant functional impairment	Hypomania only: elevated mood and energy without psychosis; functioning is not severely impaired	Hypomanic symptoms: milder fluctuations; feel like mood instability rather than a distinct disorder
Depression requirement	Not required for diagnosis, but most people experience major depressive episodes	Required: at least one major depressive episode; depression is the dominant clinical burden	Depressive symptoms present, but do not meet full criteria for a major depressive episode
Psychosis possible?	Yes — during severe manic or depressive episodes, there are hallucinations or delusions	No psychosis by definition; if present, diagnosis is revised to Bipolar I	No
U.S. prevalence	~1% lifetime	~1.1% lifetime	~0.4–1% lifetime
Key treatment focus	Mood stabilizers (lithium, valproate); antipsychotics for acute mania; psychotherapy adjunctive	Mood stabilizers (lamotrigine preferred for depression prevention); caution with antidepressant monotherapy	Mood stabilizers; psychotherapy; monitoring for progression to Bipolar I or II

Other specified and unspecified bipolar and related disorders are diagnosed when a person experiences clinically relevant episodes of abnormally elevated mood that do not meet the full duration or severity criteria for any of the three named types. This category encompasses presentations such as rapid cycling (four or more mood episodes within 12 months), bipolar with mixed features (simultaneous manic and depressive symptoms), and seasonal-pattern bipolar disorder. These presentations are clinically real and functionally impairing, even when they fall just short of formal type criteria (American Psychiatric Association, 2022).

What Are the Symptoms of Bipolar Disorder?

The symptoms of bipolar disorder differ substantially depending on the type of episode, manic, hypomanic, depressive, or mixed, and also vary between individuals and across the course of the illness. The core symptom domains are mood, energy, cognition, sleep, and behavior.

• Symptoms of a manic episode are abnormally and persistently elevated, expansive, or irritable mood; a noticeably increased level of goal-directed activity or physical energy; decreased need for sleep (feeling rested after only two to three hours); grandiosity or inflated self-esteem; racing thoughts; increased talkativeness or pressured speech (feeling compelled to keep talking); and impulsive engagement in activities with high potential for harmful consequences, such as excessive spending, reckless driving, sexual behavior outside the person’s norms, or high-risk business decisions. Full manic episodes cause deterioration and bring forth psychosis, hallucinations (perceiving things that are not present), or delusions (fixed, false beliefs) in the most severe cases (American Psychiatric Association, 2022).
• Symptoms of hypomania are qualitatively similar to mania but less severe. A person in a hypomanic episode feels unusually productive, creative, and energized, and does not recognize the episode as abnormal, or even prefers it to their baseline mood. However, hypomania is still a clinical symptom because it represents a distinct change from baseline, is observable by others, and precedes or alternates with severe depressive episodes (NIMH, 2024).
• Symptoms of a depressive episode in bipolar disorder are clinically identical to major depression: persistent sadness or emotional emptiness; loss of interest or pleasure in previously enjoyable activities (a symptom called anhedonia — from the Greek meaning “without pleasure”); changes in appetite and weight; insomnia or hypersomnia (sleeping too much); fatigue; difficulty concentrating; feelings of worthlessness or excessive guilt; and in severe cases, recurrent thoughts of death or suicidal ideation (NIMH, 2024). Bipolar depression is the dominant and most prolonged phase of the illness, particularly in Bipolar II disorder, and it is the phase during which people most seek treatment, without disclosing or remembering prior hypomanic or manic episodes.
• Symptoms of a mixed episode involve features of both mania or hypomania and major depression occurring simultaneously or within rapid succession. A person in a mixed state feels deeply dysphoric (distressed and hopeless) while also experiencing racing thoughts, agitation, and an inability to sleep. Mixed episodes are associated with elevated suicide risk because the person has both the despair that motivates suicidality and the energy and impulsivity to act on it (Oliva et al., 2024).

What Causes Bipolar Disorder?

The causes of bipolar disorder involve an interaction between genetic vulnerability, neurobiological factors, and environmental triggers. No single gene, brain abnormality, or life experience independently causes the condition — it is the convergence of multiple contributing factors in a given individual that produces the clinical syndrome.

• Genetic factors: Bipolar disorder has a heritability of approximately 60-85%, making it one of the most genetically influenced psychiatric conditions. Having a first-degree relative (parent or sibling) with bipolar disorder increases an individual’s lifetime risk approximately tenfold compared to the general population. However, the genetic architecture is complex: many common genetic variants, each with small individual effects, contribute to risk rather than a single “bipolar gene” (NIMH, 2024). This genetic complexity also explains why the condition skips generations and why identical twins, who share all genetic material, do not always both develop the condition.
• Neurobiological factors: Neuroimaging (brain scanning) studies have identified consistent structural differences in the brains of people with bipolar disorder, covering reduced gray matter volume in the prefrontal cortex (the brain’s executive control center, responsible for planning, judgment, and emotional regulation) and abnormal functioning of the amygdala (the brain’s threat and emotion detection center). Neurotransmitter systems — particularly dopamine (a brain chemical involved in reward, motivation, and mood elevation), glutamate (the brain’s primary excitatory neurotransmitter), and serotonin — show dysregulation that corresponds to episode types: dopamine overactivity is implicated in mania, while reduced serotonin and glutamate signaling are linked to depressive episodes. Circadian rhythm disruption — disruption of the body’s 24-hour internal biological clock, which governs sleep-wake cycles, hormone release, and body temperature — is a particularly well-established neurobiological feature of bipolar disorder that both predisposes to mood episodes and sustains them once triggered (Oliva et al., 2024).
• Environmental factors: Stressful life events, especially those involving loss, disruption of routine, or sleep deprivation, are among the most reliable triggers of mood episodes in genetically predisposed individuals. Sleep disruption is especially potent as a manic trigger: even a single night of lowered sleep precipitates a hypomanic or manic episode in someone with Bipolar I disorder. Substance use, particularly alcohol, cannabis, and stimulants, worsens the course of bipolar disorder by destabilizing mood, interfering with medication effectiveness, and exacerbating relapse rates. Childhood adversity and trauma are also associated with earlier onset of the disorder and a more severe clinical course (Oliva et al., 2024; NIMH, 2024).

Why Is Bipolar Disorder Difficult to Diagnose?

Bipolar disorder is difficult to diagnose because people present for treatment during depressive episodes, not manic or hypomanic ones. 

A person experiencing their first or second episode of bipolar depression receives a diagnosis of major depressive disorder (unipolar depression) because the clinician has not yet observed or elicited a history of mania or hypomania. Prior manic episodes are entirely forgotten during depressive states, have been brief enough to escape notice, or have felt so positive that the person did not mention them.

This diagnostic confusion carries a critical safety implication: antidepressant monotherapy (prescribing an antidepressant without a mood stabilizer) is a well-documented trigger of manic or hypomanic episodes in people with unrecognized bipolar disorder. NIMH explicitly cautions healthcare providers to look for signs of mania in a patient’s history before prescribing antidepressants, and Oliva et al. (2024) identify this as one of the central management challenges in the field (NIMH, 2024; Oliva et al., 2024).

Additional diagnostic challenges arise from the overlap of bipolar disorder with several other conditions that share common symptoms. Borderline personality disorder (BPD) involves emotional instability and impulsivity that resemble mixed bipolar states, but BPD mood shifts occur over hours in response to interpersonal triggers — not over days to weeks as in bipolar disorder. 

Attention-deficit/hyperactivity disorder (ADHD) and bipolar disorder frequently co-occur, and both involve distractibility, impulsivity, and sleep disruption. Post-traumatic stress disorder (PTSD) also produces the hyperarousal and emotional dysregulation that superficially resemble hypomania. A thorough psychiatric evaluation — including detailed history of all mood episodes, family history, substance use, and functional impact — is essential for accurate diagnosis (American Psychiatric Association, 2022; Oliva et al., 2024).

How Is Bipolar Disorder Treated?

The treatment of bipolar disorder is lifelong, multimodal, and individualized, meaning that no single medication or therapy works for everyone, and that treatment involves blending pharmacotherapy (medication) with psychosocial interventions to address the full range of episode types and functional consequences.

• Mood stabilizers: Lithium is the oldest and most extensively studied mood stabilizer for bipolar disorder, with strong evidence for preventing both manic and depressive episodes and for reducing suicide risk. It remains a first-line recommendation in major international treatment guidelines. Monitoring is required because lithium has a narrow therapeutic window — the difference between an effective dose and a toxic one is smaller than for most medications, requiring regular blood tests to check serum levels, kidney function, and thyroid function. Valproate (valproic acid) is an alternative mood stabilizer with particularly strong efficacy for acute mania and rapid cycling (Oliva et al., 2024).
• Lamotrigine: Lamotrigine is an anticonvulsant medication (originally developed for epilepsy) with a particular role in Bipolar II disorder and in preventing depressive episodes. It is generally better tolerated than lithium and valproate for the depressive phase of the illness. A 2025 systematic review and meta-analysis covering 10 randomized trials of 645 adults with Bipolar II assessed its comparative efficacy against lithium, reflecting the ongoing evolution of evidence for disorder-specific pharmacological guidance (Fredskild et al., 2025).
• Antipsychotic medications: Second-generation (atypical) antipsychotics — such as quetiapine, lurasidone, and olanzapine — are used both for acute manic episodes and, in some cases, for bipolar depression. Quetiapine in particular has FDA approval for both poles of bipolar disorder. Antipsychotics are used in combination with mood stabilizers, particularly when episodes are severe, involve psychosis, or are not adequately controlled by mood stabilizers alone (Oliva et al., 2024).
• Psychotherapy: Medication alone is rarely sufficient for optimal outcomes in bipolar disorder. Several psychotherapy approaches have demonstrated evidence of effectiveness as adjuncts to medication. Cognitive behavioral therapy (CBT) — a structured therapy that targets unhelpful thought patterns and behaviors — helps people identify prodromal signs (early warning indicators that a mood episode is beginning) and develop coping strategies. Interpersonal and social rhythm therapy (IPSRT) is a form of therapy developed specifically for bipolar disorder that targets circadian rhythm stabilization: helping people maintain regular sleep schedules, eating patterns, and daily routines as a biological foundation for mood stability. Psychoeducation, structured education about the condition, its triggers, and treatment, is associated with reduced relapse rates and is recommended as a standard component of bipolar care in international guidelines (Oliva et al., 2024).

When Should You Seek Help for Bipolar Disorder?

You should seek professional evaluation when you or someone you care about experiences any of the following patterns, particularly if they represent a clear departure from that person’s usual behavior:

• A distinct period of unusually elevated, expansive, or irritable mood: If elevated mood lasts more than a few days, involves decreased need for sleep, impulsive decisions, racing thoughts, or rapid speech, and is markedly different from the person’s normal baseline, this warrants prompt evaluation by a mental health professional.
• Recurrent depression that has not responded to antidepressants: If you have been prescribed antidepressants for depression and they have either not worked, produced only partial improvement, or seemed to trigger periods of unusual energy or decreased sleep, discuss the possibility of bipolar disorder with your prescribing provider before any medication changes are made.
• Family history of bipolar disorder: Given the high heritability of the condition, people with a first-degree relative with bipolar disorder should bring this history to any mental health evaluation for mood symptoms, as it substantially changes the clinical probability of a bipolar diagnosis.
• Considerable impairment during mood episodes: If mood episodes — high or low — are causing problems at work, in close relationships, with financial management, or with physical safety (including dangerous driving, sexual risk-taking, or substance use during elevated periods), a structured psychiatric evaluation is the appropriate first step.
• Thoughts of suicide or self-harm: Bipolar disorder is associated with an elevated risk of suicide, particularly during depressive and mixed episodes. If you or someone you know is having thoughts of suicide or self-harm, call or text 988 — the Suicide and Crisis Lifeline — immediately. It is free, confidential, and available 24 hours a day, 7 days a week.

The most effective first step is requesting an evaluation from a psychiatrist or licensed mental health professional with experience in mood disorders. Primary care physicians conduct initial screening and provide referrals. If the evaluation suggests bipolar disorder, a comprehensive treatment plan, combining mood-stabilizing medication with psychotherapy and structured monitoring, offers the best foundation for long-term stability.

WHAT TO DO NEXT

Bipolar disorder is a well-understood, definitively diagnosable, and effectively treatable condition. The majority of people who receive an accurate diagnosis and engage with evidence-based treatment achieve meaningful and sustained stabilization — working, maintaining relationships, and living full lives. The most consequential barrier to this outcome is diagnostic delay: getting an accurate diagnosis early and finding a prescribing clinician experienced with mood disorders is the single most important step.

If you are concerned about your own or someone else’s mental health, speak with a primary care provider, psychiatrist, or licensed mental health professional who conducts a structured assessment. If you are in crisis, call or text 988 — the Suicide and Crisis Lifeline — available 24 hours a day, 7 days a week, free and confidential.

REFERENCES

American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed., text rev.). American Psychiatric Association Publishing. https://doi.org/10.1176/appi.books.9780890425787

Fredskild, M. U., Bruun, C. F., Vinberg, M., Faurholt-Jepsen, M., Kessing, L. V., & Munkholm, K. (2025). Lithium and lamotrigine for the treatment of bipolar II disorder: A systematic review and meta-analysis of randomized trials. Journal of Affective Disorders, 383, 341–353. https://doi.org/10.1016/j.jad.2025.04.125

National Alliance on Mental Illness. (2024). Bipolar disorder. https://www.nami.org/about-mental-illness/mental-health-conditions/bipolar-disorder/

National Institute of Mental Health. (2024). Bipolar disorder. U.S. Department of Health and Human Services. https://www.nimh.nih.gov/health/topics/bipolar-disorder

National Institute of Mental Health. (2024). Bipolar disorder [Statistics]. U.S. Department of Health and Human Services. https://www.nimh.nih.gov/health/statistics/bipolar-disorder

Oliva, V., Fico, G., De Prisco, M., Fortea, L., Montejo, L., Rosa, A. R., Fuentes-Casany, J. A., Forte, M. F., Anmella, G., Hidalgo-Mazzei, D., Murru, A., Bruni, R., Sole, B., Martinez-Aran, A., Comes, M., Sanchez-Moreno, J., Carvalho, A. F., & Vieta, E. (2024). Bipolar disorders: An update on critical aspects. The Lancet Regional Health – Europe, 48, 101135. https://doi.org/10.1016/j.lanepe.2024.101135

Rowland, T. A., & Marwaha, S. (2018). Epidemiology and risk factors for bipolar disorder. Therapeutic Advances in Psychopharmacology, 8(9), 251–269. https://doi.org/10.1177/2045125318769235