Bipolar Disorder — Types I and II

• Monoaminergic Dysregulation and G-Protein Coupled Receptor Signaling: In mania, increased dopamine and norepinephrine activity in the mesolimbic and mesocortical pathways drives heightened reward sensitivity, goal-directed behavior, and impulsivity through activation of D1/D2 dopamine receptors and α1/β adrenergic receptors. These receptors couple to heterotrimeric G-proteins (Gs and Gq), activating intracellular cascades involving adenylyl cyclase, phospholipase C, and protein kinase C (PKC). Lithium and valproate both inhibit key steps in these signaling cascades—lithium inhibits inositol monophosphatase (reducing PIP2 turnover and PKC activation), while valproate increases histone deacetylase (HDAC) inhibition and alters gene expression patterns. In depressive episodes, decreased serotonergic (5-HT1A/1B receptor) and noradrenergic signaling in the prefrontal cortex and anterior cingulate impairs mood regulation and executive function, causing the observed anhedonia, negative cognition, and psychomotor retardation.

• Circadian Rhythm Dysregulation and CLOCK Gene Abnormalities: Twin and family studies have identified polymorphisms in circadian clock genes (particularly CLOCK, BMAL1, PER2, and CRY genes) as contributing to bipolar disorder susceptibility. These genes encode proteins that regulate the suprachiasmatic nucleus (SCN) master clock and downstream peripheral oscillators in mood-regulating brain regions (amygdala, prefrontal cortex, striatum). Dysregulation leads to abnormal phase relationships between central and peripheral clocks, altered melatonin and cortisol secretion patterns, and disrupted transcription of genes controlling neuroplasticity and neuroprotection. This explains why sleep deprivation can precipitate manic episodes and why sleep disruption is a prodrome to mood destabilization; conversely, maintaining regular sleep-wake cycles and using chronotherapeutic interventions (light therapy) improve outcomes.

• Intracellular Signaling Cascade Dysregulation and Neuroplasticity Deficits: Bipolar disorder involves aberrant phosphorylation cascades downstream of dopamine, serotonin, and glutamate receptors, particularly dysregulation of protein kinase A (PKA), protein kinase C (PKC), and extracellular signal-regulated kinase (ERK) pathways. These cascades normally phosphorylate transcription factors like cyclic AMP response element binding protein (CREB) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), which regulate expression of brain-derived neurotrophic factor (BDNF), glycogen synthase kinase-3 (GSK-3), and neuroprotective proteins. Bipolar disorder is characterized by reduced BDNF levels (particularly in depression), impaired neurogenesis in the hippocampus, reduced gray matter volume in the prefrontal cortex and anterior cingulate, and hyperactivity of ventral limbic structures (amygdala). Mood stabilizers like lithium act partly through GSK-3 inhibition, which increases β-catenin signaling and promotes BDNF expression and neuroplasticity; valproate similarly enhances histone acetylation, increasing expression of neuroprotective genes.

• Glutamatergic Hyperactivity and Excitotoxicity: Recent evidence suggests bipolar disorder involves glutamatergic excitotoxicity, with elevated glutamate levels in cerebrospinal fluid and elevated expression of glutamate transporters (suggesting compensatory responses to glutamate overflow). Hyperactivity of NMDA receptors and AMPA receptors on postsynaptic neurons drives excessive intracellular calcium influx, activating proteases, kinases, and apoptotic cascades that compromise neuronal function and survival. During manic episodes, glutamatergic hyperactivity may contribute to racing thoughts, flight of ideas, and impulsivity; the anticonvulsant lamotrigine, which inhibits glutamate release, has efficacy in bipolar depression, supporting this mechanism. Conversely, ketamine (NMDA antagonist) has shown rapid-acting antidepressant effects in bipolar depression, though its addictive potential limits clinical use.

• HPA Axis Hyperactivity and Stress-Related Dysregulation: Patients with bipolar disorder often show abnormal hypothalamic-pituitary-adrenal (HPA) axis function, with elevated baseline cortisol levels, blunted cortisol awakening response (CAR), and impaired dexamethasone suppression test (DST) results. Chronic HPA axis hyperactivity and elevated glucocorticoid exposure impair hippocampal function, reduce hippocampal volume, and amplify amygdala reactivity to emotional stimuli, perpetuating mood cycling. Environmental stressors (life events, trauma, sleep disruption) activate the HPA axis and interact with genetic predisposition to precipitate mood episodes, explaining why psychosocial stressors are recognized precipitants of relapse.

• Genetic and Epigenetic Contributions: Twin studies demonstrate heritability of ~80-90% for bipolar I disorder, with involvement of multiple genes of small effect (polygenic inheritance). Candidate genes include those affecting serotonin transporter (5-HTTLPR), brain-derived neurotrophic factor (BDNF Val66Met), dopamine D3 receptor, glycogen synthase kinase-3 (GSK3β), and circadian clock genes. Epigenetic mechanisms (DNA methylation, histone modifications) regulate expression of these genes and are altered by early-life adversity, trauma, and environmental stress, creating a "two-hit" model where genetic vulnerability is unmasked by environmental triggers. Copy number variations (CNVs) at loci 1q21.1, 15q11.2, 16p11.2, and 22q11.2 have been associated with increased bipolar risk, suggesting that dosage imbalance of key regulatory genes contributes to pathogenesis.

• Genetic Predisposition and Family History: The strongest risk factor is a positive family history; first-degree relatives of bipolar probands have a 5-10% lifetime risk of bipolar disorder and 20-30% risk of any mood disorder. Twin concordance for bipolar I is ~80-90% in monozygotic twins versus ~15-20% in dizygotic twins, confirming substantial heritability. Genetic variants conferring risk are distributed across multiple genes involved in neurotransmitter signaling (CACNA1C, ANK3, ODZ4), inflammatory pathways (IL1β, TNF-α), and stress response (FKBP5); the polygenic nature explains why genetic testing is not yet clinically useful for diagnosis. Consanguineous relationships and certain ancestry populations (higher rates in Indo-European populations) show higher prevalence, suggesting founder effects in some populations.

• Developmental and Environmental Risk Factors: Childhood trauma, including physical or sexual abuse, early parental loss, and severe neglect, dramatically increases bipolar disorder risk (2-5 fold) and typically leads to earlier symptom onset and greater mood instability (earlier first episode, more frequent cycling). Prenatal and perinatal complications (maternal infection, gestational diabetes, preeclampsia, low birthweight, prematurity) are associated with increased bipolar risk, likely through effects on fetal brain development and HPA axis programming. Adverse life events (bereavement, job loss, relationship dissolution, major illness) frequently precipitate the first mood episode or relapse; the timing and nature of stressors interact with circadian disruption (sleep loss, shift work, seasonal changes) to trigger acute episodes. Substance use, particularly stimulants (cocaine, methamphetamine) and hallucinogens (LSD, psilocybin), can unmask latent bipolar disorder or precipitate manic episodes in genetically predisposed individuals.

• Medical Conditions and Medication-Induced Mania: Secondary bipolar-like presentations must be excluded, including hyperthyroidism (thyroid storm mimics mania), multiple sclerosis, systemic lupus erythematosus, and CNS lesions (tumors, infections, stroke involving anterior cingulate, prefrontal cortex, or striatum). Medications that can precipitate mania include antidepressants (SSRIs, SNRIs, tricyclics—the greatest risk), corticosteroids (particularly high-dose or prolonged use), stimulant medications (methylphenidate, amphetamines), decongestants, and anesthetic agents (propofol). The "antidepressant-induced mood destabilization" phenomenon is particularly important: antidepressant monotherapy without concurrent mood stabilizer is a major trigger for mania/hypomania in bipolar-spectrum patients, and antidepressants are now contraindicated as monotherapy in Bipolar I and often avoided in Bipolar II.

• Substance Use Disorders: While not a cause per se, comorbid substance use disorder is present in 40-50% of bipolar patients, with alcohol being most common, followed by cocaine and cannabis. Substance use worsens prognosis, increases episode frequency and severity, complicates medication adherence, and increases suicide risk; onset of substance use often coincides with first mood episodes, and some evidence suggests shared genetic vulnerability (common diathesis model).

• Neurobiological Vulnerabilities: Sleep architecture abnormalities (shortened REM latency, increased REM density, decreased slow-wave sleep) precede mood episodes and represent a trait marker; any condition or behavior causing sleep deprivation (sleep apnea, irregular sleep schedule, shift work, transmeridian travel) increases relapse risk. Female-specific factors including postpartum period carry 5-10 fold increased risk of mood episodes (particularly mania/mixed episodes in first 2-4 weeks postpartum, potentially progressing to postpartum psychosis); hormonal fluctuations around menstrual cycle, oral contraceptive use, and perimenopause can destabilize mood in women with bipolar disorder.

Manic Episode (Bipolar I)

• Elevated, Expansive, or Irritable Mood (Primary Feature): The core feature is an abnormally and persistently elevated, expansive, or irritable mood lasting at least 7 consecutive days (or any duration if hospitalization is required). The mood is distinctly different from baseline euthymia, not explained by substance use or medical conditions, and causes marked functional impairment or requires hospitalization. Elevated mood may appear as euphoria, grandiosity, or infectious enthusiasm in interpersonal contexts; irritable mood predominates when the patient's grandiose plans are thwarted or challenged, creating confrontational interactions. The mood is often labile, rapidly shifting from elation to rage within minutes or hours, yet the episodic quality remains consistent.

• Flight of Ideas and Racing Thoughts (Cognitive Acceleration): Patients experience dramatically accelerated thinking with subjective sense of thoughts "racing" faster than they can articulate. This manifests as pressured speech—rapid, loud, difficult to interrupt, with frequent topic-switches and tangential associations—which represents the motor outflow of racing thoughts. Flight of ideas differs from circumstantial speech (goal-directed but with excess detail) by the loose, associative quality and inability to maintain focus; the patient may jump from discussing their plans for a clothing business to reflections on fabric physics to a business opportunity with a stranger met yesterday. This cognitive acceleration is phenomenologically distinct from the goal-directed, logical thought process of hypomanic patients or the distracted speech of ADHD.

• Grandiosity and Inflated Self-Esteem: Manic patients display pathologically increased self-esteem ranging from mild overconfidence to frank delusions of grandeur (e.g., belief in special powers, invulnerability, religious significance). Grandiosity manifests behaviorally through starting multiple ambitious projects (novel, business venture, musical composition) without realistic planning or resources, volunteering for leadership positions beyond their competence, making excessive purchases of luxury items, or taking financial risks (day trading with significant losses, large gifts to strangers). Unlike the modest overconfidence of normal mood elevation, manic grandiosity is ego-syntonic (the patient does not recognize it as excessive), resists insight, and persists despite objective evidence to the contrary.

• Decreased Need for Sleep (Not to Be Confused with Insomnia): Manic patients report feeling "rested after 2-3 hours of sleep" and do not report fatigue or the need to sleep more, contrasting sharply with the early morning awakening insomnia of depression (where sleep is interrupted) or primary insomnia (where the patient struggles to sleep but feels the need). This markedly decreased need for sleep is a cardinal feature and often a warning sign of impending mania that patients and families recognize; it is distinct from mild insomnia and represents genuine reduction in sleep need due to altered neurobiological regulation.

• Increased Goal-Directed Activity and Psychomotor Acceleration: Manic patients are characteristically hyperactive and goal-directed, with increased productivity or occupational activity (working unusually long hours, multiple projects simultaneously), increased social activity (frequent phone calls, parties, new social connections), sexual disinhibition (increased sexual activity, multiple partners, seeking novel sexual experiences), and increased risky or pleasure-seeking behavior. Psychomotor acceleration includes increased speech rate and volume, increased gesturing, and visible agitation or restlessness; the patient may pace, fidget, or appear unable to sit still despite claiming to feel energized rather than anxious.

• Distractibility and Impulsivity: Manic patients exhibit marked distractibility, with inability to filter irrelevant stimuli; a conversation is frequently interrupted by attention to background noise, visible objects, or tangential thoughts. Impulsive decision-making leads to ill-advised major life decisions made without deliberation (quitting a stable job, abrupt travel, proposing marriage to someone just met, aggressive confrontations that damage relationships). Sexual impulsivity includes decreased judgment regarding partner selection, safer sex practices, or awareness of STI risk.

• Risky and Pleasure-Seeking Behavior: Manic patients engage in markedly increased risky activities without recognition of danger, including reckless driving (speeding, ignoring traffic laws), excessive spending and financial irresponsibility (acquiring debt despite good judgment in baseline state), substance use escalation (increased alcohol, stimulants), gambling, and high-risk sexual behavior. These behaviors reflect both the impulsivity/distract

Step 1 — Establish the index mood episode (APA/DSM-5-TR)

• Manic episode: elevated/expansive or irritable mood plus increased energy or goal-directed activity, most of the day nearly every day for ≥7 days (or any duration if hospitalization is required), with ≥3 associated symptoms (≥4 if mood is only irritable) and marked impairment, psychosis, or need for hospitalization. Mnemonic DIGFAST (Distractibility, Impulsivity/Indiscretion, Grandiosity, Flight of ideas, Activity increase, Sleep need decreased, Talkativeness).
• Hypomanic episode: the same symptom menu for ≥4 consecutive days, observable by others, but without marked impairment, psychosis, or hospitalization — psychosis or hospitalization automatically upgrades the episode to mania.
• Bipolar I: a single lifetime manic episode suffices; a depressive episode is not required. Bipolar II: ≥1 hypomanic and ≥1 major depressive episode, and never a manic episode. Cyclothymic disorder: ≥2 years of subthreshold hypomanic and depressive symptoms.
• Specifiers that change management: with mixed features, rapid cycling (≥4 episodes in 12 months), with psychotic features, with peripartum onset.

Step 2 — Exclude secondary causes and substance-induced mania

• Screening labs: TSH, CMP with calcium and creatinine, CBC, urine toxicology, and hCG in any patient of childbearing potential. Neuroimaging is reserved for focal deficits, first episode after roughly age 50, or atypical features.
• Baseline before pharmacotherapy: renal function and eGFR, TSH, calcium, pregnancy test, and ECG in older patients or known cardiac disease before lithium; LFTs, CBC/platelets before valproate.

Immediate stabilization (acute mania)

• Safety first: assess suicide and homicide risk, judgment, and capacity; severe mania with psychosis, aggression, or inability to care for self warrants hospitalization, involuntary if needed.
• Stop the offender: discontinue antidepressants, stimulants, and corticosteroids where feasible; treat substance intoxication.
• Acute agitation: a second-generation antipsychotic (IM olanzapine, ziprasidone, or aripiprazole) ± a benzodiazepine (lorazepam). Avoid giving IM olanzapine together with parenteral benzodiazepines because of cardiorespiratory depression (FDA labeling).

First-line maintenance/acute mania (CANMAT/ISBD 2018; VA/DoD bipolar guideline)

• Lithium: the prototype mood stabilizer and the only agent with consistent evidence for reduction of suicide. Acts via inositol monophosphatase and GSK-3 inhibition.
• Valproate: preferred for mixed features and rapid cycling.
• Second-generation antipsychotics: quetiapine, aripiprazole, risperidone, cariprazine, asenapine — monotherapy for moderate mania, or combined with lithium/valproate for severe mania.

Bipolar depression (not the same as unipolar depression)

• Quetiapine, lurasidone, cariprazine, lumateperone, or the olanzapine–fluoxetine combination are the evidence-based choices.
• Lamotrigine: prevents depressive relapse; requires slow titration to reduce Stevens–Johnson syndrome risk, and the dose must be halved when combined with valproate (glucuronidation inhibition).

Escalation and definitive therapy

• Electroconvulsive therapy is the definitive option for treatment-refractory mania or depression, catatonia, malignant/delirious mania, high acute suicide risk, and severe episodes in pregnancy.
• Clozapine for refractory illness; adjunctive psychoeducation, family-focused therapy, interpersonal and social rhythm therapy, and rigorous sleep-schedule regularization.

Contraindicated / avoid

• Antidepressant monotherapy — precipitates manic switch and rapid cycling; use only with an antimanic agent, and avoid entirely with mixed features.
• Valproate and carbamazepine in pregnancy or in patients who may conceive — neural tube defects and impaired neurodevelopment (ACOG; FDA boxed warning); folate supplementation and contraception counseling are mandatory.
• Lithium in first trimester carries a small increase in Ebstein anomaly; drugs that raise lithium levels — NSAIDs, thiazides, ACE inhibitors/ARBs — and dehydration must be avoided.
• Carbamazepine: screen for **HLA-B*1502** in patients of Asian ancestry before use (FDA).

Disease-related

• Suicide (emergency): risk is highest in depressive and mixed episodes, where depressive hopelessness coexists with manic energy and impulsivity; any new agitation with hopelessness demands immediate risk assessment and often hospitalization. Lithium is the agent with the best antisuicide evidence.
• Psychosis and delirious (malignant) mania (emergency): mood-congruent grandiose or paranoid delusions; progression to hyperthermia, exhaustion, and autonomic instability requires ECT.
• Postpartum psychosis (emergency): abrupt onset days to weeks after delivery in a bipolar patient; confusion, delusions, infanticidal ideation — always inpatient.
• Functional and social sequelae: financial ruin, legal problems, STIs from disinhibition, comorbid substance use disorder, and progressive cognitive impairment with repeated episodes.

Treatment-related — lithium

• Lithium toxicity (emergency): precipitated by dehydration, NSAIDs, thiazides, ACE inhibitors, or acute kidney injury. Signals are coarse tremor, ataxia, dysarthria, confusion, myoclonus, seizures, and arrhythmia. Hemodialysis is the treatment for severe toxicity or renal failure; saline and drug withdrawal for milder cases.
• Nephrogenic diabetes insipidus (ADH-resistant collecting duct; polyuria, dilute urine — amiloride is the classic treatment), chronic tubulointerstitial nephropathy, hypothyroidism/goiter, and hyperparathyroidism with hypercalcemia. Monitor level, creatinine, TSH, and calcium periodically.
• Ebstein anomaly with first-trimester exposure.

Treatment-related — anticonvulsants and antipsychotics

• Valproate: hepatotoxicity and pancreatitis (boxed warning; nausea with abdominal pain plus rising transaminases or lipase), hyperammonemic encephalopathy with normal LFTs, thrombocytopenia, weight gain, PCOS-like hyperandrogenism, and neural tube defects.
• Lamotrigine: Stevens–Johnson syndrome/TEN (emergency) — any rash mandates stopping the drug; risk rises with rapid titration or concomitant valproate.
• Carbamazepine: agranulocytosis/aplastic anemia, SIADH with hyponatremia, SJS (HLA-B*1502), and CYP3A4 autoinduction that lowers levels of oral contraceptives.
• Second-generation antipsychotics: metabolic syndrome (olanzapine, quetiapine worst), hyperprolactinemia (risperidone), tardive dyskinesia, and neuroleptic malignant syndrome (emergency) — fever, lead-pipe rigidity, autonomic instability, elevated CK.

• One manic episode = Bipolar I, for life: no depressive episode is required. Bipolar II requires hypomania plus a major depressive episode and never mania.
• Psychosis or hospitalization ends the hypomania argument: by definition, either feature makes the episode manic. This is the most common distractor on Bipolar II stems.
• DIGFAST is the symptom checklist; **decreased need for sleep** (feels rested after 2–3 hours) is the discriminator from depressive insomnia and is often the earliest relapse prodrome.
• Single best next step in a depressed patient before starting an SSRI: screen for past mania/hypomania (collateral history, MDQ). Antidepressant monotherapy in bipolar disorder precipitates manic switch and rapid cycling — the classic vignette is a