Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.
Differential diagnosis and physical-health screening
Essential points for quick revision.
2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
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Acute medical or neurological mimic
Fluctuating consciousness, focal neurology, seizure, fever, severe headache, hypoxia, hypoglycaemia, postpartum confusion, intoxication or dangerous withdrawal requires emergency medical assessment before a primary depressive explanation.
Action: Use ABCDE and bedside glucose, obtain observations and a focused exposure and neurological history, treat immediate abnormalities and escalate for acute medical, obstetric or neurological care. Maintain suicide precautions and obtain collateral baseline information while the organic work-up proceeds.
Synopsis
Distinguish unipolar depression from bipolar, psychiatric, neurological, endocrine, sleep, substance and medicine-related causes through chronology, examination and targeted tests while avoiding both diagnostic overshadowing and indiscriminate screening.
Build a dated timeline of mood, biological change, function, prior episodes, activation, medical illness, reproductive events, medicines and substances.
Screen lifetime mania and hypomania before antidepressant treatment; ask about reduced sleep need, increased activity, pressured speech, confidence, irritability and risky behaviour.
Differentiate grief, adjustment disorder, anxiety, PTSD, psychotic disorders, eating disorders, neurodevelopmental conditions and personality-related difficulties by dominant pattern and course.
Key red flags
A history of mania or hypomania, antidepressant activation or episodic reduced sleep need suggests bipolar depression and changes treatment risk.
Investigation priorities
01
Longitudinal mood and activation historyFirst step
Distinguish unipolar, bipolar, substance-related and adjustment courses before treatment selection.
Management branches
Initial differentialUse course before tests
A depressive syndrome is suspected or treatment has not yet begun.
Establish chronology, previous activation, grief or trauma context, substances, medicines, physical symptoms and reproductive timing.
Perform mental-state, suicide, functional and indicated physical or neurological assessment and obtain collateral baseline evidence.
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.