Clinical Psychiatry: Core Syndromes and Differential Reasoning
Clinical Psychiatry questions reward a syndromal, longitudinal approach rather than pattern-matching single symptoms. Know the defining features and boundary conditions of the major categories: psychotic disorders (duration criteria distinguishing brief psychotic disorder, schizophreniform, and schizophrenia; the role of functional decline), mood disorders (episode type, polarity, and course specifiers such as rapid cycling and seasonal pattern), anxiety and obsessive-compulsive spectrum disorders (insight and avoidance as severity markers), trauma-related disorders (exposure criterion and timing of onset), and personality disorders (enduring, pervasive, inflexible patterns with onset in adolescence/early adulthood).
Traps
- Confusing delirium with a primary psychiatric syndrome: acute onset, fluctuating attention, and a medical cause trump any behavioral resemblance.
- Treating substance-induced presentations as primary without checking temporal relationship to intoxication or withdrawal.
- Missing that psychotic symptoms in mood disorders may be mood-congruent or mood-incongruent without changing the primary diagnosis when criteria for a mood episode are met.
- Overlooking medical mimics: thyroid disease, B12 deficiency, neurosyphilis, limbic encephalitis, and steroid-induced psychosis.
Rule of thumb
When a vignette gives you a timeline, build the diagnosis from duration first, then symptom count, then functional impact. A worked example: 3 weeks of delusions with intact function and no mood episode points to brief psychotic disorder; the same symptoms lasting 2 months with decline points to schizophrenia. Always ask what would change the diagnosis before selecting an answer.