Master Psychiatry
for USMLE Step 2 CK

Core Concepts

Psychiatry diagnoses are based on clinical assessment and the diagnostic criteria outlined in the DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, 5th Edition). Always consider the bio-psycho-social model. Key neurotransmitters involved include Dopamine (psychosis, reward), Serotonin (mood, anxiety), Norepinephrine (alertness, stress), GABA (inhibition, anxiety), and Glutamate (excitation, learning). The Mental Status Exam (MSE) is crucial: Appearance, Speech, Mood, Affect, Thought Process, Thought Content, Perception, Cognition, Insight, Judgment. Always assess suicidal and homicidal ideation (SI/HI). Risk factors for SI: SAD PERSONS (Sex, Age, Depression, Previous attempt, Ethanol/substance use, Rational thinking loss, Social supports lacking, Organized plan, No spouse, Sickness). Duty to warn/protect (Tarasoff ruling) if HI is present.

Clinical Presentation

• Mood Disorders:
  • Major Depressive Disorder (MDD): ≥5 symptoms for ≥2 weeks, including depressed mood or anhedonia. SIGECAPS: Sleep (increased/decreased), Interest (loss), Guilt/worthlessness, Energy (low), Concentration (poor), Appetite (increased/decreased), Psychomotor (agitation/retardation), Suicidal ideation.
  • Persistent Depressive Disorder (PDD/Dysthymia): Depressed mood ≥2 years (adults), ≥1 year (children/adolescents) with ≥2 other symptoms.
  • Bipolar I Disorder: ≥1 manic episode. Mania: ≥1 week of elevated/irritable mood, ≥3 DIGFAST symptoms (Distractibility, Indiscretion, Grandiosity, Flight of ideas, Activity increase, Sleep deficit, Talkativeness). Causes significant impairment.
  • Bipolar II Disorder: ≥1 hypomanic episode (<1 week, less severe, no psychosis/hospitalization) AND ≥1 major depressive episode.
• Anxiety Disorders:
  • Generalized Anxiety Disorder (GAD): Excessive worry ≥6 months, with ≥3 somatic symptoms (restlessness, fatigue, poor concentration, irritability, muscle tension, sleep disturbance).
  • Panic Disorder: Recurrent, unexpected panic attacks followed by ≥1 month of worry about future attacks or behavioral change.
  • Obsessive-Compulsive Disorder (OCD): Obsessions (recurrent intrusive thoughts) and/or Compulsions (repetitive behaviors/mental acts to reduce anxiety).
  • Post-Traumatic Stress Disorder (PTSD): Exposure to trauma, with intrusive symptoms, avoidance, negative alterations in cognition/mood, and hyperarousal symptoms for ≥1 month.
  • Social Anxiety Disorder (Social Phobia): Fear of social situations due to fear of negative evaluation.
• Psychotic Disorders:
  • Schizophrenia: ≥2 symptoms (delusions, hallucinations, disorganized speech, disorganized behavior, negative symptoms) for ≥1 month (active phase), with ≥6 months of continuous disturbance. Positive symptoms (hallucinations, delusions, disorganized speech/behavior); Negative symptoms (affective flattening, alogia, avolition, anhedonia).
  • Schizoaffective Disorder: Major mood episode concurrent with Criterion A of Schizophrenia, with delusions/hallucinations for ≥2 weeks in absence of mood symptoms.
  • Delusional Disorder: ≥1 month of ≥1 non-bizarre delusion, no other psychotic symptoms, no significant functional impairment.
• Substance Use Disorders: Characterized by impaired control, social impairment, risky use, and pharmacological criteria (tolerance/withdrawal). Specific intoxication/withdrawal syndromes (e.g., Alcohol withdrawal: tremors, seizures, delirium tremens; Opioid withdrawal: dysphoria, piloerection, diarrhea, myalgias).
• Neurocognitive Disorders:
  • Delirium: Acute onset, fluctuating course, inattention, disorganized thinking, altered consciousness. Always due to an underlying medical condition.
  • Dementia (Major Neurocognitive Disorder): Gradual onset, progressive cognitive decline in ≥1 domain (memory, language, executive function), interfering with independence. Alertness usually preserved.
• Eating Disorders:
  • Anorexia Nervosa: Restriction of energy intake leading to significantly low body weight, intense fear of gaining weight, body image disturbance.
  • Bulimia Nervosa: Recurrent binge eating and compensatory behaviors (purging, excessive exercise) at least once a week for 3 months, normal weight.
  • Binge Eating Disorder: Recurrent binge eating without compensatory behaviors, associated with distress, at least once a week for 3 months.

Diagnosis (Gold Standard)

Diagnosis is primarily clinical, based on a comprehensive psychiatric interview, MSE, and collateral information (from family/friends) to meet specific DSM-5 criteria. Crucially, always rule out general medical conditions, substance-induced causes, or other psychiatric disorders. This often involves targeted physical exam, laboratory tests (e.g., CBC, electrolytes, LFTs, TSH, B12, syphilis serology, toxicology screen), and occasionally neuroimaging (CT/MRI) if organic causes are suspected (e.g., acute change in mental status, new-onset psychosis in older adults, focal neurological signs).

Management (First Line)

Management typically involves a combination of pharmacotherapy and psychotherapy.

• MDD: Selective Serotonin Reuptake Inhibitors (SSRIs) (e.g., sertraline, escitalopram, fluoxetine) are first-line. Cognitive Behavioral Therapy (CBT) and Interpersonal Therapy (IPT) are effective psychotherapies.
• Bipolar I/II: Mood stabilizers (e.g., Lithium, Valproate, Lamotrigine, Carbamazepine) and atypical antipsychotics (e.g., quetiapine, olanzapine, risperidone, aripiprazole). Avoid antidepressants as monotherapy due to risk of mania induction.
• GAD, Panic Disorder, Social Anxiety: SSRIs/SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors) (e.g., venlafaxine, duloxetine) are first-line. CBT is highly effective. Benzodiazepines for acute anxiety attacks (short-term use only).
• OCD: SSRIs (often at higher doses than depression/anxiety), Exposure and Response Prevention (ERP), a form of CBT.
• PTSD: SSRIs/SNRIs (sertraline, paroxetine, venlafaxine). Trauma-focused CBT (e.g., Prolonged Exposure, Cognitive Processing Therapy). Prazosin for nightmares.
• Schizophrenia & other Psychotic Disorders: Atypical (2nd generation) antipsychotics (e.g., risperidone, olanzapine, quetiapine, aripiprazole) are first-line due to better side effect profile (less EPS/tardive dyskinesia). Clozapine for treatment-resistant schizophrenia.
• Alcohol Withdrawal: Benzodiazepines (e.g., lorazepam, chlordiazepoxide, diazepam) to prevent seizures/delirium tremens. Long-acting preferred for healthy liver; short-acting for liver impairment. Thiamine to prevent Wernicke-Korsakoff.
• Opioid Use Disorder: Buprenorphine/naloxone (Suboxone) or Methadone for maintenance treatment. Naloxone for overdose reversal.
• Anorexia Nervosa: Nutritional rehabilitation, refeeding (monitor for refeeding syndrome). Family-Based Treatment (FBT) for adolescents. No specific FDA-approved medication.
• Bulimia Nervosa: SSRIs (Fluoxetine is FDA-approved). CBT.
• Delirium: Treat underlying cause. Supportive care. Haloperidol for severe agitation.

Exam Red Flags