Master Psychiatry
for USMLE Step 2 CK

What the USMLE Step 2 CK Tests in Psychiatry

USMLE Step 2 CK Psychiatry tests your ability to diagnose and manage common psychiatric disorders in a clinical context, often presenting with medical or surgical co-morbidities. You must differentiate between major depressive disorder, bipolar I/II, generalised anxiety disorder, panic disorder, obsessive-compulsive disorder, post-traumatic stress disorder, schizophrenia, substance use disorders (especially alcohol, opioids, and stimulants), and neurocognitive disorders (delirium vs dementia). Questions require selecting the correct first-line pharmacotherapy (e.g., SSRIs for depression and anxiety, lithium for bipolar prophylaxis), initiating appropriate psychotherapy (CBT for OCD, exposure therapy for PTSD), and recognising emergency situations (suicide risk, serotonin syndrome, neuroleptic malignant syndrome). You must also apply DSM-5 criteria, interpret screening tools (PHQ-9, GAD-7, CAGE), and manage withdrawal syndromes (CIWA-Ar for alcohol, COWS for opioids).

High-Yield Concepts

• Major Depressive Disorder (MDD) – DSM-5 Criteria: Requires ≥5 of 9 symptoms (including depressed mood or anhedonia) present for ≥2 weeks, causing functional impairment. First-line treatment: SSRI (e.g., sertraline 50 mg daily) or SNRI; augment with bupropion or atypical antipsychotic if partial response. For severe depression with psychosis, add antipsychotic (e.g., olanzapine) or consider ECT.
• Bipolar I vs II – Core Distinction: Bipolar I requires at least one manic episode (≥1 week, elevated mood with ≥3 symptoms: grandiosity, decreased need for sleep, pressured speech, flight of ideas, distractibility, increased goal-directed activity, risky behaviour). Bipolar II requires hypomania (≥4 days) plus a major depressive episode. First-line for mania: lithium (target serum 0.6–1.2 mEq/L) or valproate; avoid antidepressants without mood stabiliser.
• Schizophrenia – Diagnosis and Management: DSM-5: ≥2 of 5 symptoms (delusions, hallucinations, disorganised speech, grossly disorganised/catatonic behaviour, negative symptoms) for ≥1 month, with continuous signs for ≥6 months. First-line: antipsychotic (e.g., risperidone 2–6 mg/day or olanzapine 10–20 mg/day). Monitor for extrapyramidal symptoms (EPS), weight gain, and QTc prolongation. Clozapine reserved for treatment-resistant cases.
• Opioid Use Disorder – Treatment Options: First-line: buprenorphine (partial agonist) or methadone (full agonist) for maintenance. For detoxification, use buprenorphine or clonidine for withdrawal symptoms. Naloxone for overdose (0.4–2 mg IV/IM, repeat q2–3 min). Do not start methadone in acute withdrawal without monitoring; risk of respiratory depression.
• Post-Traumatic Stress Disorder (PTSD) – Key Features: DSM-5: exposure to trauma, plus intrusion symptoms (flashbacks, nightmares), avoidance, negative alterations in mood/cognition, and hyperarousal (≥1 month). First-line: trauma-focused CBT or EMDR; SSRI (e.g., sertraline 50–200 mg/day) or SNRI (venlafaxine). Avoid benzodiazepines (worsen outcomes).
• Delirium vs Dementia – Differentiation: Delirium: acute onset, fluctuating consciousness, inattention, often due to medical cause (infection, electrolyte imbalance, drug toxicity). Use CAM (Confusion Assessment Method). Dementia: gradual onset, chronic, clear consciousness until late stages. First step in delirium: identify and treat underlying cause; avoid antipsychotics unless agitation is dangerous.
• Serotonin Syndrome – Diagnosis and Management: Triad: altered mental status, autonomic instability (tachycardia, hypertension, hyperthermia), neuromuscular abnormalities (clonus, hyperreflexia). Usually from combining serotonergic drugs (SSRI + MAOI, or linezolid). Treatment: stop offending agents, supportive care (cooling, benzodiazepines for seizures), cyproheptadine 12 mg PO then 2 mg q2h if severe.

Common Traps in Psychiatry Questions

• Confusing hypomania (Bipolar II) with euthymia: hypomania must include clear change in functioning and be observable by others.
• Ordering a urine drug screen for every patient with altered mental status without considering delirium due to infection or metabolic cause.
• Prescribing benzodiazepines as first-line for PTSD or panic disorder without trying SSRI/SNRI and CBT first.
• Missing the diagnosis of neuroleptic malignant syndrome (NMS) when a patient on antipsychotics presents with rigidity, fever, and elevated CK; do not give more antipsychotic.
• Assuming all patients with alcohol use disorder need detoxification: use CIWA-Ar to guide treatment; asymptomatic patients with low scores do not need benzodiazepines.
• Forgetting to screen for suicide risk in every psychiatric patient (e.g., using SAFE-T or Columbia-Suicide Severity Rating Scale) and failing to hospitalise if imminent risk.

How to Revise Psychiatry for the USMLE Step 2 CK

Prioritise DSM-5 criteria for MDD, bipolar I/II, schizophrenia, and PTSD; know first-line pharmacotherapy (SSRIs, SNRIs, lithium, antipsychotics) and when to use ECT. Questions often present as clinical vignettes with medical co-morbidity (e.g., post-MI depression, cancer-related anxiety) or in emergency settings (overdose, withdrawal). Practise differentiating delirium from dementia using CAM criteria. Memorise CIWA-Ar and COWS cut-offs for withdrawal management. Be ready to identify serotonin syndrome and NMS from drug combinations. Avoid over-reliance on benzodiazepines; recognise when CBT is indicated. Review screening tools (PHQ-9, GAD-7, CAGE) and know that first-line treatment for mild-moderate depression is psychotherapy alone. Focus on safety: suicide risk assessment and involuntary hold criteria.

Practise it: MedLumen has 50 Psychiatry questions for the USMLE Step 2 CK, each with a full explanation and references.