The reasoning (criteria in usable form)
Major depressive episode = ≥5/9 symptoms for ≥2 weeks, including ≥1 core symptom (depressed mood or anhedonia), with functional impact and exclusion of substance/medical cause. The nine: mood, anhedonia, weight/appetite change, sleep change, psychomotor agitation/retardation, fatigue, worthlessness/guilt, poor concentration, suicidal ideation (SIGECAPS + mood).
Anhedonia and pervasive low mood are the highest‑yield entry points; probe melancholic features (non‑reactive mood, early‑morning waking, diurnal variation, marked psychomotor change, profound anhedonia) because they predict biological‑treatment responsiveness.
Two things you must not skip
- Screen for bipolarity before prescribing an antidepressant. Ask every depressed patient about past periods of decreased need for sleep + elevated energy/activity. Missing this risks an antidepressant‑induced switch and mistreatment (Concept 19).
- Structured suicide risk assessment — ideation → intent → plan → means/access → prior attempts → protective factors → immediate safety. "Are you depressed?" is not a risk assessment.
Psychotic depression — recognise it
Mood‑congruent delusions (guilt, poverty, nihilistic/Cotard) or hallucinations mark a severe subtype needing antipsychotic + antidepressant (or ECT) — an antidepressant alone under‑treats it. "My organs have rotted; I am already dead" is Cotard, not pessimism.
Differential
Bipolar depression, persistent depressive disorder (dysthymia), adjustment disorder, grief, hypothyroidism/anaemia/B12, substance‑induced, dementia (pseudodementia), and medication‑induced mood change.
Pitfalls
- Treating recurrent "unipolar" depression without a bipolar screen.
- Under‑treating psychotic depression as ordinary MDD.
Pearls
- 🎯 SIGECAPS + a bipolar screen + a risk assessment = the minimum viable depression work‑up.
- 🩺 Anhedonia + melancholic features flag the patients most likely to need biological treatment.
Next → The opposite pole, where the diagnosis pivots the entire treatment strategy (Concept 18).