Bipolar and related disorders are recurrent, lifelong illnesses defined by pathological shifts in mood, energy, and goal-directed activity, with a population burden disproportionate to their prevalence because of early onset, high suicide risk, and substantial functional disability. The DSM-5-TR places bipolar I disorder, bipolar II disorder, cyclothymic disorder, substance- or medication-induced bipolar disorder, bipolar disorder due to another medical condition, other specified, and unspecified bipolar disorder in a chapter of their own, positioned between schizophrenia spectrum and depressive disorders to reflect their phenomenological and genetic links to both. The diagnostic threshold turns on the presence and duration of mania or hypomania — a single manic episode is sufficient for bipolar I, while bipolar II requires at least one hypomanic and one major depressive episode without ever crossing into mania. Most of the lifetime symptom burden is depressive, not manic, which is why bipolar depression is routinely misdiagnosed as unipolar depression and treated with antidepressant monotherapy that can destabilize the illness. Lithium remains the cornerstone mood stabilizer for relapse prevention and is the only agent with consistent anti-suicide signal across studies. The bottom line: every patient presenting with depression deserves a careful screen for past hypomania or mania before treatment is chosen.

Bipolar disorder is uncommon but globally distributed, with onset clustered in adolescence and young adulthood and a heavy comorbidity burden that shapes both prognosis and treatment selection.

Prevalence and onset

• Lifetime prevalence in the World Mental Health Surveys is approximately 0.6% for bipolar I, 0.4% for bipolar II, and 1.4% for subthreshold bipolar, with twelve-month prevalence roughly half those figures.¹
• Mean age of onset is in the late teens to early twenties, with a substantial proportion experiencing first symptoms before age 18.²
• Onset after age 50 is uncommon and should prompt a search for a medical, neurologic, or substance-related cause.³

Sex and sociodemographic patterns

• Bipolar I prevalence is approximately equal across sexes, while bipolar II and rapid-cycling presentations are more common in women.^1-2
• Women are more likely to experience depressive episodes, mixed features, and rapid cycling; men present more often with manic episodes and comorbid substance use.²

Comorbidity

• More than 60% of individuals with bipolar disorder meet criteria for at least one anxiety disorder during the lifetime.¹
• Substance use disorders co-occur in roughly 40-60% and worsen course, adherence, and suicide risk.⁴
• ADHD, eating disorders, and personality disorders (particularly borderline personality disorder) are frequent and complicate the diagnostic picture.²
• Cardiovascular disease, metabolic syndrome, and obesity are markedly more prevalent than in the general population and contribute to a 10- to 15-year reduction in life expectancy.⁵

Suicide risk

• Lifetime suicide attempt rates exceed 30%, and completed suicide accounts for an estimated 6-7% of deaths, with risk highest during depressive and mixed states.⁶

Risk factors

• First-degree family history of bipolar disorder is the strongest known risk factor, with heritability estimates of 70-85%.⁷
• Childhood adversity, particularly emotional and sexual abuse, is associated with earlier onset, greater symptom severity, and higher suicidality.⁸
• Cannabis use, sleep disruption, and stimulant exposure are associated with onset and recurrence in vulnerable individuals.⁵

Bipolar disorder is a polygenic, neurodevelopmental illness with abnormalities spanning monoaminergic and glutamatergic signaling, intracellular second-messenger systems, circadian regulation, and large-scale brain networks. No single mechanism explains the phenotype; current models emphasize gene-environment interaction over a single neurotransmitter lesion.

Genetics

• Twin studies estimate heritability at 70-85%, among the highest in psychiatry.⁷
• Genome-wide association studies have identified more than 60 risk loci, with substantial polygenic overlap with schizophrenia and major depressive disorder.⁹
• Risk variants implicate calcium channel signaling (CACNA1C), neurotransmitter regulation (ANK3), and synaptic and circadian genes.⁹

Neurotransmitter and intracellular signaling

• Dopaminergic hyperactivity in mesolimbic circuits is implicated in mania, while dopaminergic hypoactivity has been linked to bipolar depression — a "dopamine dysregulation" model consistent with the efficacy of dopamine antagonists for mania and dopamine agonists (with risk of switch) for depression.¹⁰
• Glutamatergic abnormalities, including elevated cortical glutamate during mania and altered NMDA receptor function, underlie interest in ketamine and related agents.¹¹
• Lithium and valproate converge on intracellular targets including Glycogen synthase kinase-3 and inositol monophosphatase, supporting a "second-messenger" rather than purely synaptic model.¹²

Circuits and imaging

• Structural MRI shows reduced prefrontal and hippocampal volumes and ventricular enlargement, with progressive changes related to episode burden.¹³
• Functional imaging demonstrates hyperactivity of the amygdala and ventral striatum and hypoactivity of ventrolateral and dorsolateral prefrontal cortex during emotional tasks, consistent with impaired top-down emotion regulation.¹³
• Disruption of the default mode network and salience network connectivity is observed across mood states.¹⁴

Circadian and chronobiological factors

• Sleep loss can precipitate mania, and circadian rhythm instability is a core feature; mood stabilizers and chronotherapeutic interventions act in part through circadian pathways.¹⁵

Inflammation and metabolic factors

• Elevated peripheral inflammatory markers (CRP, IL-6, TNF-α) are observed during acute episodes, and metabolic comorbidity may share mechanistic ground with the illness itself rather than being purely iatrogenic.¹⁶

The DSM-5-TR organizes bipolar and related disorders around the presence, severity, and duration of mood episodes. Mania is the diagnostic threshold for bipolar I; hypomania plus a major depressive episode defines bipolar II; subthreshold but persistent mood instability defines cyclothymia.

Manic episode

• A distinct period of abnormally elevated, expansive, or irritable mood with persistently increased goal-directed activity or energy, lasting at least one week (or any duration if hospitalization is required).¹⁷
• During the period, three or more of the following are present (four if mood is only irritable): inflated self-esteem or grandiosity, decreased need for sleep, pressured speech, flight of ideas or racing thoughts, distractibility, increased goal-directed activity or psychomotor agitation, and excessive involvement in activities with high potential for painful consequences.¹⁷
• The disturbance causes marked impairment, necessitates hospitalization, or includes psychotic features; it is not attributable to a substance or another medical condition.¹⁷

Hypomanic episode

• The same symptom criteria as mania, but the duration requirement is at least four consecutive days, and the change in functioning is observable to others without causing marked impairment, hospitalization, or psychotic features.¹⁷
• The presence of psychosis or hospitalization automatically reclassifies the episode as manic, regardless of duration.¹⁷

Major depressive episode in bipolar disorder

• Five or more depressive symptoms (depressed mood, anhedonia, weight or appetite change, sleep disturbance, psychomotor retardation or agitation, fatigue, worthlessness or guilt, impaired concentration, suicidal ideation) over a two-week period, with at least one being depressed mood or anhedonia.¹⁷
• Phenomenologically indistinguishable from unipolar depression at the cross-sectional level, though atypical features, psychomotor retardation, hypersomnia, and earlier onset are more common in bipolar depression.¹⁸

Bipolar I disorder

• Requires a single lifetime manic episode; depressive episodes are common but not required for diagnosis.¹⁷

Bipolar II disorder

• Requires at least one hypomanic and one major depressive episode, with no history of mania.¹⁷
• Should not be conceptualized as a milder form of bipolar I; depressive burden, suicidality, and functional impairment can be equivalent or greater.¹⁹

Cyclothymic disorder

• At least two years (one year in children and adolescents) of numerous periods of hypomanic and depressive symptoms that do not meet full episode criteria, present at least half the time and never absent for more than two months.¹⁷

Other bipolar variants

• Substance- or medication-induced bipolar disorder requires symptoms developing during or shortly after substance use, including antidepressant-induced mood elevation in some clinical contexts.¹⁷
• Bipolar disorder due to another medical condition requires direct pathophysiologic linkage to a medical illness (e.g., hyperthyroidism, multiple sclerosis, traumatic brain injury, stroke).¹⁷
• Other specified and unspecified bipolar disorder cover presentations that do not meet full duration or symptom criteria but cause clinically significant distress or impairment.¹⁷

DSM-5-TR specifiers

• With anxious distress, with mixed features, with rapid cycling, with melancholic features, with atypical features, with mood-congruent or mood-incongruent psychotic features, with catatonia, with peripartum onset, and with seasonal pattern.¹⁷
• Mixed features (depressive symptoms during a manic or hypomanic episode, or three manic symptoms during a depressive episode) replaced the older DSM-IV "mixed episode" and broadened the construct.¹⁷
• Rapid cycling: four or more mood episodes in twelve months, meeting full criteria for any of mania, hypomania, or major depression.¹⁷

ICD-11 differences

• ICD-11 retains bipolar type I and II as separate categories and explicitly recognizes mixed episodes as a coding option, more closely resembling DSM-IV than DSM-5-TR on that point.²⁰
• ICD-11 places greater emphasis on increased activity or energy as a core diagnostic feature, mirroring the DSM-5-TR shift away from mood elevation as the sole gateway symptom.²⁰

Bipolar disorder is best characterized as a recurrent illness with a depressive center of gravity punctuated by manic, hypomanic, and mixed episodes, against a background of subsyndromal symptoms and inter-episode functional impairment. Recognizing the full phenotype matters: the prototypical "happy mania" is less common than irritable, mixed, or psychotic presentations.

Manic phenomenology

• Mood is classically euphoric or expansive but is irritable in 40-50% of presentations and frankly dysphoric in mixed states.²¹
• Pressured speech, flight of ideas, and goal-directed hyperactivity are highly characteristic; disinhibited spending, hypersexuality, and reckless driving are common harms.²¹
• Decreased need for sleep — distinct from insomnia — is a sensitive prodromal sign.²²
• Psychotic features occur in roughly half of manic episodes and may be mood-congruent (grandiose delusions) or mood-incongruent (paranoid or bizarre delusions, Schneiderian first-rank symptoms).²¹

Depressive phenomenology

• Bipolar depression more often features hypersomnia, hyperphagia, leaden paralysis, and psychomotor retardation than agitation.¹⁸
• Atypical features and psychotic features are more common than in unipolar depression.¹⁸
• Suicidal ideation and attempts cluster in depressive and mixed states, not in pure mania.⁶

Mixed states

• Co-occurring opposite-polarity symptoms (e.g., depressed mood with racing thoughts and agitation, or elevated mood with profound dysphoria) carry the highest near-term suicide risk and are notoriously difficult to treat.²³

Course features

• A prodromal phase of mood lability, sleep disturbance, anxiety, or attenuated symptoms often precedes a full episode by months to years.²
• Inter-episode recovery is often incomplete; subsyndromal depressive symptoms dominate the inter-episode period and account for much of the functional impairment.²⁴
• Cognitive deficits in attention, processing speed, working memory, and executive function persist between episodes, particularly in patients with more episodes or psychotic features.²⁵

Red flags suggesting bipolarity in a depressed patient:

• Early onset of first depression (under age 25).¹⁹
• Multiple depressive episodes, particularly with brief inter-episode intervals.¹⁹
• Family history of bipolar disorder, completed suicide, or psychiatric hospitalization.¹⁹
• Antidepressant-induced mood elevation, agitation, or rapid response followed by loss of effect.¹⁹
• Postpartum onset of severe depression with psychotic features.²⁶
• Atypical features, psychomotor retardation with hypersomnia, or psychotic features in a depressive episode.¹⁸

Bipolar disorder is misdiagnosed for years on average, most often as unipolar depression, and a structured differential is the only reliable defense against that error. Phenocopies span psychiatric, medical, neurologic, and substance-induced conditions.

Psychiatric differentials

• Major depressive disorder: distinguished by the absence of any past hypomanic or manic episode; careful collateral history is essential because hypomania is poorly recalled.¹⁹
• Schizoaffective disorder: requires at least two weeks of psychosis without prominent mood symptoms during the lifetime course; bipolar with psychotic features does not.¹⁷
• Schizophrenia: psychosis dominates the longitudinal course with relatively brief mood episodes; affective flattening rather than mood elevation predominates.¹⁷
• Borderline personality disorder: mood shifts occur over hours, are reactive to interpersonal stressors, and lack the sustained sleep change and grandiosity of hypomania.²⁷
• ADHD: distractibility, talkativeness, and impulsivity are chronic and trait-like rather than episodic, though comorbidity is common, particularly in pediatric populations.²⁸
• Substance use disorders: stimulants, cocaine, and synthetic cathinones can mimic mania; cannabis and hallucinogens can produce psychosis.²⁹
• Anxiety disorders: panic attacks and generalized anxiety can produce sleep loss and racing thoughts but lack mood elevation, grandiosity, and goal-directed hyperactivity.⁵

Medical and neurologic mimics

• Hyperthyroidism, Cushing syndrome, and corticosteroid exposure can produce manic-like presentations.³⁰
• Multiple sclerosis, traumatic brain injury, stroke (particularly right-sided), brain tumors (frontal and temporal), HIV, and neurosyphilis can produce secondary mania.³⁰
• Delirium can mimic agitated mania; the hallmark is fluctuating attention and altered consciousness.⁴²
• Temporal lobe epilepsy can produce ictal or interictal mood and behavioral disturbances.³⁰

Substance- and medication-induced presentations

• Stimulants (amphetamines, methylphenidate, cocaine), corticosteroids, dopamine agonists, levodopa, and certain antibiotics (e.g., quinolones, isoniazid) can precipitate manic-like states.³¹
• Antidepressant-induced mania in a patient without prior bipolar history is itself a marker of bipolar diathesis under DSM-5-TR.¹⁷

Mnemonic for secondary mania workup

Diagnosis is clinical, anchored by a careful longitudinal history with collateral, supported by validated screening tools and a focused medical workup. No biomarker or imaging finding is diagnostic.

Interview approach

• Establish a lifetime episode timeline; mood charts and life-event anchors substantially improve recall of past hypomanic episodes.³²
• Ask about decreased need for sleep, increased goal-directed activity, and behavioral consequences (spending, sexual, legal) — patients are more likely to report behaviors than mood states.²
• Obtain collateral from a partner or family member whenever possible; hypomania is frequently ego-syntonic and underreported.²
• Screen every depressed patient for past mania or hypomania before initiating treatment.¹⁹

Mandatory history elements

• Age at first mood symptom and first full episode.²
• Number, duration, and polarity of past episodes; presence of mixed, rapid-cycling, or psychotic features.¹⁷
• Prior treatment trials, response, and tolerability, including any antidepressant-associated activation or mood elevation.¹⁹
• Family history of bipolar disorder, depression, suicide, and substance use.⁷
• Substance use, including caffeine, nicotine, alcohol, cannabis, and stimulants.²⁹
• Suicide history: ideation, intent, plan, prior attempts, lethality, and access to means.⁶
• Trauma history, including childhood adversity.⁸
• Sleep, circadian patterns, and recent shift work or travel.¹⁵
• Reproductive status and contraception in patients of childbearing potential, given teratogenicity of several mood stabilizers.³³

Validated rating scales

• Young Mania Rating Scale (YMRS): clinician-administered, 11 items; standard for mania severity in trials and clinics.³⁴
• Mood Disorder Questionnaire (MDQ): self-report screen for lifetime hypomania or mania; sensitivity is moderate, specificity acceptable in clinical settings.³⁵
• Bipolar Spectrum Diagnostic Scale (BSDS) and Hypomania Checklist-32 (HCL-32) are alternative screens with broader sensitivity for bipolar II.³⁶
• Hamilton Depression Rating Scale (HAM-D) and Montgomery-Asberg Depression Rating Scale (MADRS) for depressive severity tracking.^25,53
• Columbia Suicide Severity Rating Scale (C-SSRS) for structured suicide risk assessment.⁵¹

Physical exam

• Vital signs, weight and BMI, neurologic exam, and inspection for signs of substance use, self-injury, or medical mimics (goiter, cushingoid features).⁵

Labs and baseline workup

• CBC, comprehensive metabolic panel, TSH, fasting glucose and lipid panel, urine toxicology, and pregnancy test in patients of childbearing potential.³⁷
• ECG before initiating antipsychotics with QT-prolonging potential or in patients with cardiovascular risk.³⁷
• Lithium-specific baseline: TSH, BUN/creatinine and eGFR, electrolytes, calcium, urinalysis, weight, and ECG in patients over 40 or with cardiac risk.³⁸
• Valproate-specific baseline: CBC with platelets, LFTs, weight, and pregnancy test; ammonia if encephalopathy is suspected.³⁹
• Carbamazepine-specific: CBC, LFTs, sodium, and HLA-B*1502 testing in individuals of Asian ancestry due to Stevens-Johnson syndrome risk.⁴⁰

Imaging

• Neuroimaging (MRI preferred over CT) is not routine but is indicated for first episode in older adults, focal neurologic findings, atypical presentation, or treatment resistance.³⁴
• EEG is reserved for suspected seizure activity or atypical episodic phenomena.⁴²

What NOT to order

• Genetic testing for bipolar risk variants is not clinically indicated outside research settings.⁹
• Neuropsychological testing is not required for diagnosis; reserve for documenting cognitive impairment that affects function or treatment planning.²⁵

Treatment is phase-specific: acute mania, acute bipolar depression, and maintenance follow distinct evidence bases, and the agents that work in one phase may worsen another. The overarching goals are rapid containment of the acute episode, prevention of switch, and long-term relapse prevention with the lowest sustainable burden of medication.

Pharmacotherapy

Acute mania

• Strong evidence supports lithium, valproate, and second-generation antipsychotics (risperidone, olanzapine, quetiapine, aripiprazole, asenapine, cariprazine, ziprasidone, paliperidone) as first-line monotherapy for acute mania.^42-43
• Combination therapy (lithium or valproate plus a second-generation antipsychotic) is recommended for severe mania, psychotic features, or partial response to monotherapy and produces faster and larger effect sizes than monotherapy.^42-43
• Carbamazepine is an effective second-line option, particularly for mixed or rapid-cycling presentations, but is limited by drug interactions and adverse effects.⁴³
• Haloperidol is highly effective acutely but carries higher rates of extrapyramidal symptoms and post-mania depression than second-generation agents.⁴⁴
• Antidepressants should be tapered and discontinued during acute mania.⁴²
• Benzodiazepines (lorazepam, clonazepam) are useful adjuncts for agitation and sleep restoration but are not primary mood-stabilizing agents.⁴²

Acute bipolar depression

• Quetiapine, lurasidone, cariprazine, and the olanzapine-fluoxetine combination have FDA approval for bipolar I depression based on placebo-controlled trials.⁴⁵
• Lumateperone has FDA approval for depressive episodes in bipolar I and II, including as adjunct to lithium or valproate.⁴⁶
• Lamotrigine has limited acute antidepressant efficacy but evidence supports its role in maintenance, particularly for depressive relapse prevention.⁴⁷
• Lithium has moderate evidence for acute bipolar depression and stronger evidence for relapse prevention; it remains first-line when broader maintenance protection is the goal.⁴²
• Adjunctive antidepressants are controversial: CANMAT and ISBD guidance permits cautious use of SSRIs or bupropion in bipolar II depression in combination with a mood stabilizer; tricyclics and SNRIs (particularly venlafaxine) carry higher switch risk and should be avoided when possible.⁴⁸
• Antidepressant monotherapy is contraindicated in bipolar I and discouraged in bipolar II.⁴⁸

Maintenance

• Strong evidence supports lithium for relapse prevention, particularly of manic episodes, with the most robust anti-suicide signal of any psychiatric medication.^49-50
• Quetiapine, aripiprazole (including long-acting injectable), olanzapine, and lamotrigine have evidence for maintenance, with lamotrigine especially effective against depressive relapse and weaker against mania.^42-43
• Valproate is widely used in maintenance, though randomized maintenance evidence is less robust than for lithium.⁵¹
• Long-acting injectable antipsychotics (aripiprazole monohydrate, risperidone, paliperidone palmitate) are increasingly used in patients with adherence concerns.³⁴
• Combination maintenance is common in clinical practice but increases adverse-effect burden; periodic attempts at simplification are warranted.⁴²

Therapeutic monitoring

• Lithium: maintain serum levels of 0.6-1.0 mEq/L for maintenance and 0.8-1.2 mEq/L for acute mania, drawn 12 hours after the last dose; check levels every 5-7 days during titration, then every 3-6 months.³⁸
• Valproate: target serum levels of 50-125 µg/mL for mood stabilization; monitor LFTs, CBC with platelets, and weight.³⁹
• Carbamazepine: target 4-12 µg/mL; monitor CBC, LFTs, and sodium for hyponatremia.⁴⁰

Psychotherapy

• Evidence supports adjunctive psychotherapy in combination with pharmacotherapy; it does not replace mood stabilizers.⁵²
• Cognitive behavioral therapy (CBT): moderate evidence for relapse prevention and depressive symptom reduction.⁵²
• Interpersonal and social rhythm therapy (IPSRT): targets circadian and social rhythm regularity; moderate evidence for relapse prevention.³⁴
• Family-focused therapy: reduces relapse and improves functional outcome, with the strongest evidence in adolescents and recent-onset patients.³⁴
• Psychoeducation, individual or group, improves medication adherence, early-warning-sign recognition, and relapse rates.³⁴
• Dialectical behavior therapy adaptations have preliminary evidence for emotion dysregulation and suicidality in bipolar disorder.³⁴

Neuromodulation

• Electroconvulsive therapy (ECT) is highly effective for severe mania, severe bipolar depression, mixed states, catatonia, peripartum presentations, and treatment-resistant illness, with response rates often exceeding pharmacotherapy.³³
• ECT is the treatment of choice when rapid response is required (suicidality, refusal to eat or drink, pregnancy in which medication exposure is undesirable).³³
• Repetitive transcranial magnetic stimulation has limited evidence in bipolar depression compared with unipolar; it is an option in treatment-resistant cases but not first-line.³⁴
• Vagus nerve stimulation is FDA-cleared for treatment-resistant depression including bipolar depression but is rarely used given access and evidence limitations.³⁴

Adjunctive

• Sleep stabilization, light exposure regularity, and avoidance of shift work and trans-meridian travel during vulnerable periods are core behavioral interventions.¹⁵
• Substance use treatment is integral; untreated substance use is among the strongest predictors of relapse and treatment failure.⁴
• Thyroid optimization is reasonable in rapid-cycling patients, with some evidence for high-dose levothyroxine adjunctive therapy.³⁴
• Omega-3 fatty acids have weak evidence for bipolar depression and are a reasonable low-risk adjunct.³⁴
• N-acetylcysteine and inositol have been studied as adjuncts with mixed results.³⁴

The therapeutic burden in bipolar disorder is substantial: most patients require lifelong medication, and the agents that work carry meaningful adverse effects. The evidence base, while extensive for acute mania, is thinner for bipolar depression and bipolar II.

Common adverse effects

• Lithium: tremor, polyuria and polydipsia, weight gain, hypothyroidism, hyperparathyroidism, acne, and cognitive complaints.^27,38
• Valproate: weight gain, alopecia, tremor, sedation, GI upset, and menstrual irregularity including polycystic ovary syndrome.³⁹
• Second-generation antipsychotics: weight gain, dyslipidemia, hyperglycemia, sedation, akathisia, and hyperprolactinemia (most prominently risperidone and paliperidone).³⁰
• Lamotrigine: rash (most cases benign), headache, dizziness, and diplopia.⁴⁷
• Carbamazepine: dizziness, ataxia, sedation, hyponatremia, and a wide range of drug interactions through CYP induction.⁴⁰

Serious or rare adverse effects

• Lithium toxicity: tremor, ataxia, confusion, seizures, and arrhythmia at supratherapeutic levels; chronic toxicity can produce irreversible cerebellar damage (SILENT syndrome).³⁸
• Long-term lithium use is associated with reduced eGFR and a small but real risk of progression to chronic kidney disease.²⁷
• Valproate hepatotoxicity, hyperammonemic encephalopathy (with or without elevated LFTs), pancreatitis, and thrombocytopenia.³⁹
• Carbamazepine: agranulocytosis, aplastic anemia, Stevens-Johnson syndrome, and toxic epidermal necrolysis (HLA-B*1502 marker in Asian ancestry).⁴⁰
• Lamotrigine: Stevens-Johnson syndrome and toxic epidermal necrolysis with rapid titration or after recent rash; require slow titration and immediate discontinuation if rash develops.⁴⁷
• Antipsychotics: tardive dyskinesia, neuroleptic malignant syndrome, QT prolongation, and metabolic syndrome.³⁰
• Clozapine, used off-label for treatment-resistant bipolar disorder, requires hematologic monitoring for agranulocytosis.²⁷

Monitoring, withdrawal, and discontinuation

• Lithium: monitor levels every 3-6 months once stable; check renal function, TSH, and calcium every 6-12 months.³⁸
• Valproate: monitor levels, LFTs, CBC, and weight at baseline, during titration, and periodically thereafter.³⁹
• Antipsychotics: monitor weight, BP, fasting glucose, and lipids per ADA/APA consensus schedule.³⁰
• Abrupt lithium discontinuation is associated with high rates of manic relapse; taper over weeks when discontinuation is necessary.^34,50
• Anticonvulsant discontinuation should also be gradual to reduce relapse and rebound risk.³⁴

Limitations of the evidence

• Most maintenance trials are 6-24 months in duration, limiting inference about decades-long management.⁴²
• Many bipolar depression trials use enriched designs that may inflate effect estimates.³⁶
• Patients with substance use disorders, suicidality, and significant medical comorbidity are systematically excluded from RCTs, limiting generalizability.³⁴
• Bipolar II is comparatively understudied; treatment recommendations are often extrapolated from bipolar I trials.¹⁹
• Long-term comparative effectiveness data favor lithium, but lithium is increasingly underprescribed.⁵⁰

Bipolar disorder presents and is treated differently across the lifespan and across reproductive, medical, and cultural contexts. Treatment selection is shaped as much by who the patient is as by which episode they are in.

Pediatric

• Pediatric bipolar I disorder is rare but recognized; phenomenology more often features irritability, mixed features, and rapid mood shifts than classic euphoric mania.⁴⁴
• Severe non-episodic irritability, previously labeled "pediatric bipolar disorder" by some groups, is now categorized as Disruptive mood dysregulation disorder under depressive disorders in DSM-5-TR to discourage overdiagnosis of bipolarity.¹⁷
• Risperidone, aripiprazole, asenapine, olanzapine, and quetiapine are FDA-approved for pediatric bipolar mania, generally at lower doses than in adults.³⁴
• Lithium is approved for pediatric mania from age 7 and remains a useful agent.³⁴
• Family-focused therapy and psychoeducation have the strongest psychotherapy evidence in this group.³⁴

Geriatric

• Late-onset mania (after age 50) should prompt evaluation for secondary causes, particularly cerebrovascular disease, neurodegenerative illness, and medication effects.³
• Older adults are more sensitive to lithium toxicity at any given level due to reduced renal clearance and altered volume of distribution; target lower levels and monitor more frequently.³⁸
• Antipsychotic use in older adults with dementia carries a black-box warning for increased mortality.³⁰

Perinatal

• Pregnancy and the postpartum period are high-risk windows; up to 50% of women with bipolar disorder relapse postpartum, and the first month postpartum carries the highest lifetime risk of psychiatric hospitalization.²⁶
• Lithium in the first trimester is associated with a small absolute increase in cardiac malformations (Ebstein anomaly historically, though more recent data suggest a smaller effect than originally reported); risk-benefit decisions are individualized.⁴⁶
• Valproate is contraindicated in pregnancy when avoidable due to neural tube defects, craniofacial malformations, and lasting cognitive impairment in offspring.³³
• Carbamazepine and topiramate also carry teratogenic risk.³³
• Lamotrigine has a relatively favorable reproductive safety profile.³³
• Many second-generation antipsychotics have accumulating reassuring data, though long-term neurodevelopmental data are limited.³⁵
• ECT is safe and effective in pregnancy and is preferred when rapid response is needed and medication exposure is undesirable.³³

Comorbid medical illness

• Renal impairment: prefer non-lithium options or use lithium with careful monitoring at lower target levels.³⁸
• Cardiovascular disease: monitor QTc with antipsychotics; avoid agents with high QT-prolonging potential when possible.³⁰
• Hepatic disease: avoid valproate when significant hepatic dysfunction is present.³⁹
• Metabolic syndrome: prefer agents with lower metabolic burden (lurasidone, lumateperone, aripiprazole, ziprasidone) when feasible.³⁰
• Epilepsy: anticonvulsant mood stabilizers (valproate, lamotrigine, carbamazepine) offer dual benefit.²⁷

Comorbid substance use

• Integrated treatment of mood and substance use produces better outcomes than sequential approaches.⁴
• Lithium has evidence for reducing alcohol use in adolescents with bipolar disorder; valproate and quetiapine have additional supportive data.³⁴
• Naltrexone, acamprosate, and disulfiram can be used for comorbid alcohol use disorder; buprenorphine and methadone for comorbid opioid use disorder.²⁷

Cultural considerations

• Idioms of distress and culturally shaped presentations of mania (e.g., religious or grandiose content) require culturally informed assessment.¹
• HLA-B*1502 testing before carbamazepine initiation is particularly important in patients of Han Chinese, Thai, Filipino, Malaysian, Indonesian, and other Asian ancestries.⁴⁰
• Access disparities and stigma shape both diagnosis and treatment in many populations.³⁵

Bipolar disorder is a chronic, recurrent illness. With consistent treatment, most patients achieve remission of acute episodes; sustained euthymia and full functional recovery are harder to attain.

Natural history

• Without treatment, episodes typically recur, with cycle length shortening and inter-episode intervals narrowing over time in a subset of patients (the "kindling" hypothesis, though contested).⁵
• The depressive pole accounts for the majority of symptomatic time across the lifetime, particularly in bipolar II.²⁴
• Subsyndromal symptoms persist between episodes in a majority of patients and contribute to ongoing functional impairment.²⁴

Response and remission

• Acute manic response rates with first-line monotherapy are approximately 50% at 3 weeks; combination therapy increases response.⁴²
• Acute bipolar depression remission rates with current first-line agents are 30-50%, lower than rates achieved in mania.⁴⁵
• Long-term euthymia is achieved in a minority; recurrence over 5 years exceeds 70% even with treatment.⁴⁹

Suicide risk over the lifetime

• Lifetime suicide attempt prevalence is over 30%, with completed suicide accounting for 6-7% of deaths.⁶
• Suicide risk is highest during depressive and mixed states and within the first year of illness; protective factors include lithium use and active treatment engagement.⁵⁰

Functional outcome

• Even with mood remission, fewer than half of patients achieve full functional recovery within 2 years of an episode.¹⁸
• Cognitive impairment, particularly in attention, processing speed, and executive function, predicts functional outcome independent of mood symptoms.²⁵

Mortality

• All-cause mortality is increased approximately twofold compared with the general population, with cardiovascular disease as the leading non-suicide cause of premature death.⁵
• Average life expectancy is reduced by 10-15 years.⁵

Acute mania, severe mixed states, and bipolar depression with high suicide risk are psychiatric emergencies. The decision points are containment, safety, and stabilization, in that order.

Hospitalization criteria

• Imminent risk of harm to self or others.⁴²
• Severe mania with psychotic features, agitation, or inability to maintain safety.⁴²
• Mixed states with prominent suicidality.²³
• Severe bipolar depression with psychotic features or refusal to eat or drink.⁴²
• Inability to participate in outpatient treatment due to symptom severity, comorbid substance use, or lack of supports.⁴²
• Catatonia.⁴²

Acute agitation management

• Verbal de-escalation and environmental management are first-line.⁴²
• For pharmacologic management, intramuscular formulations of olanzapine, aripiprazole, ziprasidone, or haloperidol, with or without lorazepam, are commonly used; avoid combining intramuscular olanzapine with parenteral benzodiazepines due to risk of cardiorespiratory depression.^27,54
• Inhaled loxapine is an alternative for cooperative patients with acute agitation.⁵⁴

Suicide risk markers

• Depressive or mixed state, hopelessness, prior attempts, recent discharge, comorbid substance use, comorbid borderline personality features, and recent psychosocial loss.⁶
• Lithium maintenance is associated with reduced suicide attempts and completions and should be specifically considered in high-risk patients.⁵⁰

Postpartum considerations

• The first 30 days postpartum carry the highest lifetime risk of psychiatric hospitalization in women with bipolar disorder; Postpartum psychosis requires immediate evaluation and is most often a manifestation of bipolar disorder.²⁶

Clinical practice in bipolar disorder is shaped by several long-running debates that affect prescribing daily.

Antidepressants in bipolar depression

• Whether antidepressants should ever be used in bipolar depression remains contested; meta-analyses suggest modest acute efficacy but limited long-term benefit and risk of mood destabilization, particularly in bipolar I and rapid cycling.^36-37
• The ISBD task force discourages antidepressant monotherapy and recommends combination with a mood stabilizer when used at all.³⁶
• Practice varies internationally, with North American guidelines more permissive than several European recommendations.^34-35

Bipolar II as a milder variant

• Bipolar II is sometimes framed as a milder form of bipolar I, but longitudinal data show comparable depressive burden, comparable suicide risk, and substantial functional impairment.^18,52
• Whether bipolar II warrants the same maintenance pharmacotherapy as bipolar I is unsettled, particularly for lithium versus lamotrigine.³⁴

Bipolar spectrum and soft signs

• Some authors advocate for a broader bipolar spectrum that includes hyperthymic temperament, antidepressant-induced hypomania, and brief hypomanic episodes shorter than four days.⁵
• Critics caution that broadening the construct risks overdiagnosis and inappropriate exposure to mood stabilizers and antipsychotics.⁵
• DSM-5-TR retained the four-day threshold for hypomania and the requirement that antidepressant-emergent hypomania persisting beyond physiological effect counts toward bipolar diagnosis.¹

Mixed features versus mixed episode

• DSM-IV required full criteria for both mania and depression simultaneously; DSM-5-TR replaced the mixed episode with a mixed-features specifier requiring three contrapolar symptoms.¹
• Some clinicians find the new specifier more sensitive but less specific, capturing agitated unipolar depression and complicating treatment selection.¹

Pediatric bipolar disorder

• Rates of pediatric bipolar diagnosis rose sharply in the United States in the 1990s and 2000s, prompting concern about overdiagnosis of irritable, dysregulated children.⁴⁴
• DSM-5 introduced disruptive mood dysregulation disorder partly to redirect such presentations away from a bipolar diagnosis; long-term outcome data continue to accumulate.^1,44

Ketamine and esketamine

• Ketamine and esketamine show rapid antidepressant effects in unipolar depression, but evidence in bipolar depression is limited and the risk of treatment-emergent affective switch in bipolar populations is not fully characterized.³⁴

• A single lifetime manic episode is sufficient to diagnose bipolar I disorder; a depressive episode is not required.¹
• Hypomania requires at least four consecutive days of symptoms with observable change in functioning, but no marked impairment, no psychosis, and no hospitalization.¹
• Antidepressant-emergent hypomania or mania that persists beyond the physiological effect of treatment counts toward a bipolar diagnosis under DSM-5-TR.¹
• Mean age of onset for bipolar I is approximately 18 years; bipolar II onset is typically in the mid-twenties.⁵
• Lifetime suicide attempt rates approach 30-40% in bipolar disorder, and standardized mortality from suicide is roughly 10-20 times the general population.^6-7
• Lithium has the strongest evidence for relapse prevention and is the only agent with a consistent anti-suicide signal across studies.^34,50
• Lithium maintenance therapeutic range is 0.6-1.0 mEq/L for most patients, with levels up to 1.2 mEq/L acceptable acutely; toxicity emerges above 1.5 mEq/L.²⁷
• Quetiapine, olanzapine-fluoxetine combination, lurasidone, cariprazine, and lamotrigine (maintenance only) are first-line options for bipolar depression; lamotrigine is not effective for acute mania.^32,34
• Valproate is teratogenic (neural tube defects, neurodevelopmental harm) and should be avoided in females of reproductive potential when alternatives exist.^28,46
• Carbamazepine induces CYP3A4 and reduces the efficacy of oral contraceptives, lamotrigine, and many other drugs.²⁹
• Antidepressant monotherapy is contraindicated in bipolar I depression; if used in bipolar depression at all, antidepressants should be combined with a mood stabilizer or antimanic antipsychotic.³⁶
• ECT is highly effective in severe, psychotic, catatonic, or treatment-resistant mania and bipolar depression and is the preferred option in pregnancy when rapid response is needed.³³
• Postpartum psychosis is most often a manifestation of bipolar disorder; the first 30 days postpartum carry the highest lifetime psychiatric admission risk in affected women.²⁶
• Cyclothymic disorder requires at least two years (one in youth) of fluctuating hypomanic and depressive symptoms that do not meet threshold for full episodes.¹
• Rapid cycling is defined as four or more mood episodes within 12 months and is associated with female sex, hypothyroidism, and antidepressant exposure.²⁰
• The Mood Disorder Questionnaire is a screening tool for bipolarity in patients presenting with depression; a positive screen requires diagnostic confirmation.²⁴

No external funding. No conflicts of interest declared. Peer-review status: pending.