Major depressive disorder Study Guide

📖 Core Concepts Major Depressive Disorder (MDD) – ≥2 weeks of pervasive low mood or loss of pleasure, plus ≥4 other symptoms (e.g., sleep change, appetite change, guilt). Core symptoms: depressed mood or anhedonia. Epidemiology: 2 % of world population; peak onset in the 20s; women ≈3 × more likely than men. Subtypes/Specifiers (DSM‑5): melancholic, atypical, catatonic, anxious distress, peripartum, seasonal affective disorder. Pathophysiology: monoamine deficits (serotonin, norepinephrine, dopamine), HPA‑axis dysregulation, reduced hippocampal volume, inflammatory markers (CRP, IL‑6). Course: single episode → recurrent episodes (≈80 % will have ≥1 additional episode); severe/psychotic → 90 % recurrence. Treatment hierarchy: psychotherapy + antidepressant (first‑line); somatic options (ECT, rTMS, ketamine) for treatment‑resistant or severe cases. Recovery & relapse prevention: continue medication ≥6 months after remission; maintenance CBT/MBCT further lowers relapse. --- 📌 Must Remember DSM‑5/ICD‑11 requirement: 5 / 9 symptoms, ≥1 core, 2 weeks, functional impairment. Severity specifiers: mild (≤2 symptoms beyond core), moderate (3–4), severe (≥5 or psychotic features). First‑line meds: SSRIs (e.g., sertraline, escitalopram) – best tolerated. Continuation therapy: ≥6 months (reduces relapse 70 %). Recurrence risk: 30 % within 1 yr; 50 % within 2 yr; 90 % for psychotic depression. Screening: USPSTF – screen all ≥12 yr when follow‑up resources exist (use PHQ‑9, BDI, HAM‑D). Suicide risk: ↑ in males (higher completion) and in adolescents/young adults on antidepressants (black‑box warning). Key lab exclusions: TSH, electrolytes, CBC, vitamin D, testosterone (men). --- 🔄 Key Processes Diagnostic Work‑up Clinical interview → mental‑state exam → rule‑out medical mimics (labs, imaging). Apply DSM‑5 criteria → assign severity/specifier. Use rating scales (PHQ‑9, HAM‑D) for baseline severity. Pharmacotherapy Initiation Choose SSRI → start low dose, titrate over 4‑6 weeks. Assess response at 6‑8 weeks; if <50 % improvement → switch or augment. For non‑response: switch to another SSRI/SNRI or add bupropion/lithium. Psychotherapy Integration Offer CBT or IPT alongside meds for moderate–severe MDD. For children/adolescents → psychotherapy first; meds only if inadequate response. Escalation to Somatic Treatments Treatment‑resistant (≥2 adequate trials) → consider rTMS, ketamine, or ECT. ECT protocol: 2–3 sessions/week × 6–12 treatments; maintain meds afterwards. Maintenance & Relapse Prevention Continue med ≥6 months after remission; consider 12 months for high‑risk patients. Add maintenance CBT/MBCT for recurrent depression. --- 🔍 Key Comparisons SSRIs vs. Tricyclic Antidepressants (TCAs) Efficacy: comparable for moderate‑severe MDD. Side‑effects: SSRIs = milder; TCAs = anticholinergic, cardiac toxicity. Melancholic vs. Atypical Depression Mood reactivity: absent in melancholia, present in atypical. Sleep: early‑morning awakening (melancholia) vs. hypersomnia (atypical). Weight: loss (melancholia) vs. gain (atypical). ECT vs. rTMS Indication: ECT – severe/psychotic or rapid response needed; rTMS – treatment‑resistant, less invasive. Side‑effects: ECT – transient memory loss; rTMS – scalp discomfort, rare seizures. Pharmacotherapy alone vs. Combined with Psychotherapy Outcome: combined yields higher remission rates and lower relapse. --- ⚠️ Common Misunderstandings “Depression = sadness” – MDD can present with irritability, somatic complaints, or no obvious sadness. “Antidepressants work instantly” – therapeutic effect usually appears after 4–6 weeks. “Only severe cases need medication” – mild‑moderate depression also benefits, especially with functional impairment. “All patients need lifelong meds” – many can discontinue after 6–12 months if fully remitted and low risk of recurrence. --- 🧠 Mental Models / Intuition “5‑of‑9 rule” – picture a checklist of nine symptoms; any 5 (including a core) = MDD. “Stress‑vulnerability cascade” – genetics (30‑40 %) + life stress → HPA‑axis overload → neuroplastic changes (hippocampal shrinkage) → depressive episode. “Treatment ladder” – start low (psychotherapy + SSRI), step up (switch/augment), jump to somatic (rTMS/ECT) if stuck. --- 🚩 Exceptions & Edge Cases Post‑partum depression – onset during pregnancy or ≤1 month postpartum; hormonal trigger. Seasonal Affective Disorder – requires ≥2 depressive episodes in winter/spring with remission in opposite season, lasting ≥2 years. Atypical depression – mood reactivity preserved; may respond better to MAOIs (historically) or SSRIs with added bupropion. Children/adolescents – higher suicide risk with SSRIs; psychotherapy preferred first. Elderly – more somatic symptoms, higher hyponatremia risk with SSRIs; choose agents with minimal anticholinergic load. --- 📍 When to Use Which Mild, recent onset, good support → psychotherapy alone or lifestyle (exercise). Moderate‑severe, functional impairment → SSRI + psychotherapy. Psychotic features, urgent response needed → ECT (with informed consent). Treatment‑resistant after ≥2 meds → rTMS → ketamine/​esketamine → ECT. Seasonal pattern → light therapy ± antidepressant. Comorbid chronic pain → consider SNRIs (e.g., venlafaxine) or add duloxetine. --- 👀 Patterns to Recognize Diurnal variation – early‑morning awakening → melancholic subtype. Mood reactivity + weight gain + hypersomnia → atypical depression. Psychomotor agitation/retardation + non‑reactive mood → melancholia. Suicidal ideation + psychotic delusions → psychotic depression (requires urgent ECT/​meds). Somatic complaints + normal affect in collectivist cultures → possible depression masquerading as physical illness. --- 🗂️ Exam Traps “Any two‑week low mood qualifies as MDD.” – must have ≥5 symptoms and functional impairment. “SSRIs are always first‑line for every patient.” – contraindicated in certain populations (e.g., children with high suicide risk, severe hepatic disease). “Atypical depression never responds to SSRIs.” – many patients improve; MAOIs are not the only option. “Normal grief = MDD.” – bereavement lacks pervasive guilt, self‑devaluation, and usually resolves within 2 months. “Hyponatremia is only a concern with TCAs.” – SSRIs have a higher incidence of SIADH‑related hyponatremia, especially in older adults. ---