System 10 · ~9% of exam
Psychiatry
Diagnostic criteria matter. Duration thresholds. Safety assessment first. Know the first-line medications and their side effects, and when therapy beats medication.
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Chief complaints
BUILD THE DIFFERENTIAL
Vignettes enter through one of these doors. Each complaint lays out the full differential, marks the can't-miss diagnoses, and tells you the next right action for each.
CHIEF COMPLAINT · HIGH-YIELD
Depressed mood
Safety first. Then differentiate MDD from bipolar, grief, medical, substance-induced.
Approach
SIG E CAPS for 2 weeks = MDD. Bipolar if history of mania/hypomania. Grief follows loss and is proportionate. Medical mimics: hypothyroidism, anemia, B12, vitamin D, steroids, interferon. Substance: alcohol, cocaine withdrawal, benzos. Always assess suicidality.
The differential
| Diagnosis | Key features / clues | Next step |
|---|---|---|
| Suicide risk requiring admission | Plan, intent, access to means, recent attempt, command hallucinations. | Ensure safety · hospitalize if imminent risk · remove means · activate supports |
| Major depressive disorder | 5 of 9 SIG E CAPS for ≥ 2 weeks, with anhedonia or depressed mood. Functional impairment. | SSRI (first-line) · CBT · consider therapy alone for mild |
| Bipolar depression | Current depression with history of mania (≥ 7 days) or hypomania (≥ 4 days). | Mood stabilizer (lithium, valproate, lamotrigine) · quetiapine or lurasidone for bipolar depression · AVOID antidepressant monotherapy |
| Persistent depressive disorder | Chronic (≥ 2 years) low-grade depression, fewer symptoms than MDD. | SSRI + therapy |
| Adjustment disorder | Depression in response to identifiable stressor within 3 months. | Therapy · time-limited · supportive |
| Grief | Follows a loss, comes in waves, positive memories, not pervasive anhedonia. | Supportive · refer if complicated grief or prolonged > 12 months |
| Hypothyroidism / medical | Fatigue, cold intolerance, weight gain, bradycardia. | TSH · treat underlying |
⚑ = can't-miss diagnosis · rule out first
Classic vignette
Exam-style stem
A 32-year-old woman has 6 weeks of fatigue, anhedonia, insomnia, 10 lb weight loss, difficulty concentrating, feelings of worthlessness. Denies suicidal thoughts. No history of mania. TSH normal.
Best initial treatment?
Answer › SSRI (sertraline, escitalopram, or fluoxetine) plus CBT. Response assessed at 4–6 weeks. Full remission target. Continue for 6–12 months after remission for first episode.
Pearls
Pearl
SSRI black box warning for suicidality in patients < 25. Monitor closely in first month.
Pearl
Never give antidepressant monotherapy in bipolar disorder, risk of mania induction. Mood stabilizer first.
Pearl
Failure to respond to adequate trial (8 weeks of therapeutic dose) of one SSRI: switch to another SSRI or SNRI, or augment with bupropion, mirtazapine, or atypical antipsychotic.
CHIEF COMPLAINT · HIGH-YIELD
Anxiety
Chronic excessive worry is GAD. Discrete attacks are panic. Situation-specific is phobia/social.
Approach
Medical workup first in new anxiety: thyroid, cardiac, pheochromocytoma, substance (caffeine, cocaine). CBT + SSRI/SNRI for most anxiety disorders. Benzos short-term only.
The differential
| Diagnosis | Key features / clues | Next step |
|---|---|---|
| Generalized anxiety disorder | Excessive worry most days for ≥ 6 months, difficult to control, with 3 of 6 symptoms (restlessness, fatigue, concentration, irritability, muscle tension, sleep). | CBT · SSRI or SNRI (sertraline, escitalopram, venlafaxine, duloxetine) · buspirone adjunct |
| Panic disorder | Recurrent unexpected panic attacks + 1 month of worry about attacks or behavior change. Symptoms: palpitations, dyspnea, chest pain, sweating, depersonalization, fear of dying. | CBT · SSRI · short course of benzos (bridge) |
| PTSD | Trauma exposure + intrusion + avoidance + negative mood + arousal for > 1 month. | Trauma-focused CBT or EMDR · SSRI (sertraline, paroxetine FDA-approved) · prazosin for nightmares |
| OCD | Obsessions + compulsions, time-consuming (> 1 hour/day) or impairing. | Exposure and response prevention · SSRI at higher doses · clomipramine |
| Social anxiety disorder | Fear of scrutiny in social situations for > 6 months. | CBT · SSRI · beta-blocker (propranolol) for performance anxiety |
| Medical/substance | New anxiety in older adult, rapid onset, associated symptoms (palpitations, HTN). | TSH, thyroid panel · cardiac workup · tox screen · pheochromocytoma workup if clues |
⚑ = can't-miss diagnosis · rule out first
Pearls
Pearl
Benzodiazepines are effective fast but should be short-term only (weeks) due to tolerance and dependence. Long-term management is SSRI + therapy.
Pearl
Prazosin reduces PTSD nightmares. Add to regular PTSD treatment if nightmares are prominent.
Pearl
Buspirone is non-sedating and non-addictive. Useful adjunct or alternative in GAD but takes weeks for effect.
CHIEF COMPLAINT
Psychosis
Primary (schizophrenia, schizoaffective, bipolar) vs secondary (medical, substance).
Approach
Rule out secondary causes: substance intoxication/withdrawal, medication, medical (thyroid, B12, syphilis, HIV, autoimmune encephalitis, brain tumor). First episode: hospitalize, start antipsychotic, medical workup.
The differential
| Diagnosis | Key features / clues | Next step |
|---|---|---|
| Schizophrenia | ≥ 6 months of symptoms including ≥ 1 month of positive symptoms (delusions, hallucinations, disorganized speech), ± negative symptoms. Functional decline. | Atypical antipsychotic (risperidone, olanzapine, aripiprazole) · psychosocial interventions · clozapine for refractory |
| Schizoaffective | Psychosis + mood episodes, with ≥ 2 weeks of psychosis without mood. | Antipsychotic + mood stabilizer or antidepressant |
| Brief psychotic disorder | < 1 month, often after severe stressor. | Short-term antipsychotic · therapy |
| Bipolar with psychotic features | Mania or severe depression with psychosis. | Mood stabilizer + antipsychotic |
| Substance-induced | During intoxication or withdrawal. Cocaine, meth, cannabis, PCP, alcohol. | Supportive · benzodiazepines · resolve with substance clearance |
| Delirium | Acute, fluctuating, inattention, altered LOC. Elderly, medical illness. | Treat underlying · haldol or quetiapine only if dangerous agitation |
⚑ = can't-miss diagnosis · rule out first
Pearls
Pearl
First-episode psychosis: full medical workup. Young patient with new psychosis, think autoimmune encephalitis (anti-NMDA), substance, medical.
Pearl
Clozapine for treatment-resistant schizophrenia. Watch agranulocytosis (weekly CBC), myocarditis, seizure, metabolic syndrome. The most effective antipsychotic but the most monitoring.
Pearl
First-generation antipsychotics have higher EPS risk: acute dystonia (hours-days, give benztropine or diphenhydramine), akathisia (restlessness, beta-blocker), parkinsonism, tardive dyskinesia (late, sometimes permanent).
CHIEF COMPLAINT · HIGH-YIELD
Substance use
Screen universally. Recognize intoxication and withdrawal syndromes. Address comorbid psych.
Approach
Alcohol: CIWA for withdrawal, long-term naltrexone or acamprosate. Opioids: methadone or buprenorphine maintenance, naloxone. Benzos: taper slowly to avoid seizures. Cocaine: supportive. Tobacco: varenicline or bupropion or nicotine replacement.
The differential
| Diagnosis | Key features / clues | Next step |
|---|---|---|
| Alcohol withdrawal / DTs | 6–48 hrs: tremor, anxiety, tachycardia. 48–96 hrs: seizures, DTs (tachy, HTN, fever, hallucinations, delirium). | Benzodiazepines (CIWA-guided) · thiamine + folate · electrolyte repletion · ICU for DTs |
| Opioid overdose | Miotic pupils, respiratory depression, bradycardia. | Naloxone · support ventilation · observe for recurrent toxicity |
| Opioid withdrawal | Yawning, lacrimation, rhinorrhea, diarrhea, piloerection, pupillary dilation, myalgias. Not life-threatening in healthy adults. | Buprenorphine or methadone induction · clonidine, loperamide, ondansetron for symptoms |
| Benzodiazepine overdose | Sedation, ataxia, slurred speech. Respiratory depression with co-ingestion. | Supportive · flumazenil only in naive overdose (precipitates seizures in chronic users) |
| Stimulant intoxication (cocaine, meth) | Tachycardia, HTN, mydriasis, agitation, psychosis, chest pain. | Benzodiazepines · avoid beta-blockers (unopposed alpha vasoconstriction) |
| Alcohol use disorder | ≥ 2 of 11 criteria over 12 months. | Motivational interviewing · naltrexone or acamprosate · disulfiram (supervised) |
| Opioid use disorder | DSM criteria. Often chronic. | Buprenorphine-naloxone or methadone (MAT) · naloxone prescription · harm reduction |
⚑ = can't-miss diagnosis · rule out first
Pearls
Pearl
Alcohol withdrawal: benzodiazepines are first-line and only evidence-based. DTs have up to 5% mortality untreated.
Pearl
Wernicke encephalopathy triad (confusion + ataxia + ophthalmoplegia): IV thiamine BEFORE glucose in any alcoholic or malnourished patient with AMS.
Pearl
Methamphetamine use is rising. Presents with cardiovascular complications, psychosis, meth mouth. No FDA-approved treatment for stimulant use disorder.
✦
Disease deep dives
DEFINITIVE DX
Once you've identified the likely diagnosis from the chief complaint, these pages give you the presentation, workup, management, and exam pearls in depth.
Major Depressive Disorder
Biopsychosocial illness. SSRIs and CBT are first-line. Safety first.
Bipolar Disorder
Mania (bipolar I) or hypomania (bipolar II) defines. Mood stabilizers are foundation.
Schizophrenia
Positive, negative, cognitive symptoms. Dopamine blockade is the foundation of treatment.
Anxiety Disorders
GAD, panic, phobias, social anxiety, PTSD, OCD. SSRIs + CBT.
Substance Use Disorders
Recognize withdrawal syndromes. Medication-assisted treatment for opioids and alcohol.
DISEASE DEEP DIVE
Major Depressive Disorder
Biopsychosocial illness. SSRIs and CBT are first-line. Safety first.
Presentation
≥ 2 weeks of depressed mood or anhedonia, plus ≥ 4 of: sleep change, appetite/weight change, psychomotor changes, fatigue, guilt/worthlessness, concentration, suicidal ideation.
Workup
- PHQ-9. Screening and severity. Used to track response.
- Rule out medical mimics. TSH, CBC, B12, vitamin D, medication review.
- Safety assessment. Suicidal ideation, plan, intent, means, prior attempts. Access to firearms.
Management
- Mild. CBT or SSRI. Patient preference.
- Moderate to severe. SSRI + CBT is more effective than either alone.
- First-line SSRIs. Sertraline, escitalopram, fluoxetine. Start low, titrate to therapeutic dose, assess response at 4–6 weeks.
- Non-response. Switch SSRI, switch class (SNRI like venlafaxine or duloxetine), augment with bupropion/mirtazapine/lithium/atypical antipsychotic.
- Severe / psychotic / catatonic. Consider ECT (often first-line for severe, psychotic, catatonic, pregnant, rapid response needed).
- Maintenance. Continue for 6–12 months after remission for first episode. Indefinite for recurrent or severe.
Pearls
Pearl
SSRI side effects: sexual dysfunction, GI, insomnia or sedation, weight gain. Serotonin syndrome if combined with other serotonergic agents (triptans, tramadol, MAOIs).
Pearl
Bupropion: avoid in seizure disorder, eating disorders. Less sexual dysfunction, sometimes weight loss. Also used for smoking cessation.
Pearl
Mirtazapine: useful if insomnia or poor appetite (side effects become therapeutic).
DISEASE DEEP DIVE
Bipolar Disorder
Mania (bipolar I) or hypomania (bipolar II) defines. Mood stabilizers are foundation.
Presentation
Mania: ≥ 7 days of elevated/irritable mood + DIG FAST (Distractibility, Impulsivity, Grandiosity, Flight of ideas, Activity increase, Sleep decrease, Talkative). Severe, psychosis, hospitalization common. Hypomania: ≥ 4 days, less severe, no hospitalization/psychosis.
Workup
- Clinical. Mood history, functional impact.
- Rule out. TSH, substance use, medication-induced (steroids, antidepressants).
Management
- Acute mania. Lithium, valproate, or atypical antipsychotic (risperidone, olanzapine, quetiapine, aripiprazole). Combine if severe.
- Bipolar depression. Quetiapine, lurasidone, lamotrigine, or lithium. AVOID antidepressant monotherapy.
- Maintenance. Lithium, valproate, lamotrigine (better for depression), atypical antipsychotics.
- Lithium monitoring. Narrow therapeutic window (0.6–1.2). Check level, creatinine, TSH every 6 months. Avoid NSAIDs, thiazides, ACEi.
- Valproate cautions. Hepatotoxicity, pancreatitis, thrombocytopenia, teratogenic (neural tube defects). Avoid in pregnancy.
Pearls
Pearl
Lithium toxicity: tremor, ataxia, confusion, seizures. Precipitants: dehydration, NSAIDs, ACEi, thiazides. Hemodialysis for severe toxicity.
Pearl
Lamotrigine: Stevens-Johnson syndrome. Titrate slowly. Useful for bipolar depression maintenance.
Pearl
Rapid cycling: ≥ 4 mood episodes in 12 months. Often worsens with antidepressants. Mood stabilizer only.
DISEASE DEEP DIVE
Schizophrenia
Positive, negative, cognitive symptoms. Dopamine blockade is the foundation of treatment.
Presentation
Positive: hallucinations, delusions, disorganized speech/behavior. Negative: flat affect, avolition, alogia, anhedonia. Cognitive: memory, executive function. Onset typically late teens to late twenties.
Workup
- Clinical diagnosis. ≥ 2 symptoms (one must be hallucination, delusion, or disorganized speech) for ≥ 6 months with ≥ 1 month active phase. Functional decline.
- Rule out medical. Tox screen, TSH, B12, syphilis, HIV, head imaging if new-onset or atypical.
Management
- Antipsychotic. Atypical (second-generation) first-line: risperidone, olanzapine, aripiprazole, quetiapine. Ziprasidone, paliperidone, lurasidone alternatives.
- Long-acting injectable. For adherence issues. Risperidone, paliperidone, aripiprazole, haloperidol decanoate.
- Clozapine. For treatment-resistant (failure of 2 antipsychotics). Most effective but most monitoring: weekly CBC first 6 months for agranulocytosis.
- Psychosocial. Family therapy, supported employment, assertive community treatment, cognitive remediation.
Pearls
Pearl
First-generation antipsychotics (haloperidol, fluphenazine, chlorpromazine), more EPS. Second-generation, more metabolic (weight gain, DM, lipids).
Pearl
Neuroleptic malignant syndrome: fever, rigidity (lead pipe), autonomic instability, altered mental status, elevated CK. Stop antipsychotic, supportive care, dantrolene or bromocriptine.
Pearl
Metabolic monitoring for atypicals: weight, lipids, glucose at baseline, 3 months, annually.
DISEASE DEEP DIVE
Anxiety Disorders
GAD, panic, phobias, social anxiety, PTSD, OCD. SSRIs + CBT.
Presentation
Varies by disorder. Common: excessive worry, avoidance, autonomic arousal, impairment.
Workup
- Clinical diagnosis. DSM criteria. Rule out medical (thyroid, cardiac, pheochromocytoma).
- Screening. GAD-7, PHQ-9 (depression comorbidity), PC-PTSD-5.
Management
- CBT. First-line for most anxiety disorders. Exposure therapy for phobias and OCD. Trauma-focused CBT for PTSD.
- SSRI or SNRI. First-line pharmacotherapy. Often combined with CBT.
- Benzodiazepines. Short-term only, especially for panic disorder bridging. Avoid in substance use disorder history.
- Specific. Prazosin for PTSD nightmares. Beta-blocker for performance anxiety. Buspirone for GAD augmentation. SSRIs at higher doses for OCD.
Pearls
Pearl
Panic attack vs panic disorder: panic attacks can occur in many disorders (MDD, PTSD, specific phobia). Panic disorder requires recurrent unexpected attacks + ≥ 1 month worry or behavior change.
Pearl
Generalized anxiety disorder is highly comorbid with MDD. Treat both.
DISEASE DEEP DIVE
Substance Use Disorders
Recognize withdrawal syndromes. Medication-assisted treatment for opioids and alcohol.
Presentation
DSM criteria: ≥ 2 of 11 over 12 months. Range from mild (2–3) to severe (≥ 6).
Workup
- Screening. AUDIT, DAST, CAGE, SBIRT framework.
- Labs. LFTs, CBC, hepatitis panel, HIV. BAL, utox.
Management
- Alcohol use disorder. Naltrexone (reduces cravings, blocks reward), acamprosate (reduces protracted withdrawal cravings), disulfiram (aversive therapy, requires commitment). Topiramate and gabapentin off-label.
- Opioid use disorder. Buprenorphine-naloxone (can be prescribed in office, partial agonist, ceiling effect on respiratory depression), methadone (full agonist, clinic-based), naltrexone (for motivated patients post-detox). Naloxone prescription for overdose.
- Tobacco use disorder. Varenicline (most effective monotherapy), bupropion, nicotine replacement therapy. Combine NRT types (patch + gum).
- Alcohol withdrawal. CIWA-guided benzodiazepines. Thiamine + folate + multivitamin. ICU for severe withdrawal or DTs.
Pearls
Pearl
Buprenorphine can precipitate withdrawal if given too early. Wait until moderate withdrawal (COWS score) to induct.
Pearl
Naltrexone is contraindicated if opioid use within 7–10 days. Will precipitate severe withdrawal.
Pearl
Motivational interviewing (open questions, affirmations, reflections, summaries) is more effective than confrontation.