A 38-year-old woman presents to the psychiatry outpatient clinic with a 3-month history of persistent low mood, anhedonia, and difficulty concentrating at work. She reports waking up at 4 AM every morning and being unable to return to sleep. Her appetite has decreased significantly, and she has lost 6 kg unintentionally. She denies any suicidal ideation but expresses hopelessness about her future. On mental status examination, her speech is slow and her affect is flat. She has no significant past psychiatric history. What is the most likely diagnosis based on DSM-5 criteria?

Explanation

## Diagnostic Reasoning **Key Point:** Major Depressive Disorder (MDD) is diagnosed when ≥5 symptoms of depression are present for ≥2 weeks, causing clinically significant distress or impairment, and are not attributable to substance use, medical illness, or bereavement. ### Symptom Count in This Case This patient meets the following criteria: 1. Depressed mood (low mood for 3 months) 2. Anhedonia (loss of interest/pleasure) 3. Sleep disturbance (early morning awakening at 4 AM — a feature of melancholic depression) 4. Concentration difficulty 5. Appetite/weight loss (6 kg unintentional) 6. Psychomotor retardation (slow speech, flat affect) 7. Hopelessness (negative cognition) Total: **7 symptoms** — well above the threshold of 5. **Duration:** 3 months (exceeds the 2-week minimum). **Severity Assessment:** With 7 symptoms and functional impairment at work, this meets **moderate severity** criteria (≥5 symptoms, marked distress, moderate functional impairment). ### Why This Is NOT the Other Diagnoses | Feature | MDD (Moderate) | Dysthymia | Adjustment Disorder | Bipolar II | |---------|---|---|---|---| | Duration | ≥2 weeks | ≥2 years | <3 months post-stressor | Depressive episode ≥2 weeks | | Symptom count | ≥5 | ≥2–3 (milder) | Fewer, mild–moderate | ≥5 for depression | | Onset | Acute/subacute | Insidious, chronic | Clear stressor | Preceded by hypomanic episode | | This case | ✓ Acute 3-month onset, 7 symptoms | ✗ Too severe, too acute | ✗ No clear stressor mentioned | ✗ No hypomanic history | **High-Yield:** Early morning awakening (terminal insomnia) is a hallmark of **melancholic depression** — a specifier within MDD that indicates biological/endogenous features and often predicts better response to antidepressants and ECT. **Clinical Pearl:** The presence of psychomotor retardation (slow speech, flat affect) and vegetative symptoms (sleep, appetite, energy) suggests a more severe, endogenous presentation — consistent with moderate MDD rather than mild or adjustment-related depression. **Mnemonic: SIGECAPS** — Mnemonic for MDD symptoms: - **S**leep disturbance - **I**nterest loss (anhedonia) - **G**uilt / worthlessness - **E**nergy loss / fatigue - **C**oncentration difficulty - **A**ppetite change - **P**sychomotor change - **S**uicidal ideation This patient has S, I, E, C, A, P — **6 of 8 SIGECAPS** (no guilt/worthlessness explicitly stated, no suicidal ideation).