Psychiatry: Description, Risk, and Differentiating Syndromes
Priority concepts
Expect the mental state examination in structured form: appearance and behaviour, speech, mood and affect, thought form and content, perception, cognition, insight, and risk. Know the diagnostic building blocks of depression, mania, psychosis, anxiety, and substance withdrawal, plus the interface between physical and mental health.
Delirium, dementia, and depression overlap and are tested together. Delirium is acute, fluctuating, and characterised by inattention with altered consciousness. Dementia is chronic and progressive with preserved consciousness until late. Depression can produce reversible cognitive slowing that mimics dementia.
Traps
Risk assessment is never answered by 'the patient denied intent and was discharged'. Documented risk factors - previous attempts, access to means, male sex, substance use, living alone, recent loss - matter more than reassurance in the moment. Also watch for questions that conflate akathisia with worsening agitation; adding antipsychotics to undiagnosed akathisia is the wrong move.
Worked example
A patient on a serotonergic antidepressant develops tremor, clonus, hyperreflexia, and fever over 24 hours. This is serotonin syndrome rather than neuroleptic malignant syndrome, which evolves over days with lead-pipe rigidity and marked autonomic instability. Stop the offending agent, provide supportive care, and consider benzodiazepines; cyproheptadine is an option in moderate to severe cases.
Rule of thumb
Before accepting a functional explanation, exclude common mimics: hypoglycaemia, hypoxia, infection in the elderly, thyroid disease, medication effects, and substance withdrawal. Sudden behavioural change in an older inpatient is delirium until proven otherwise - find the cause.