Psychopathology and Diagnostic Formulation
Core concepts
Candidates must use precise phenomenological language. Key distinctions: delusion (fixed false belief, held with conviction, not shared by culture) versus overvalued idea (understandable, less fixed); illusion (misperception of real stimulus) versus hallucination (perception without stimulus); pseudohallucination (in inner space, recognised as unreal); thought insertion/withdrawal/broadcast as passivity phenomena; formal thought disorder (derailment, loosening, neologisms) versus circumstantiality and tangentiality. Distinguish obsessions (ego-dystonic, resisted) from delusional and impulsive phenomena.
Formulation
A good formulation integrates predisposing, precipitating, perpetuating and protective factors (the 4Ps), links them to a differential diagnosis, and states a management plan. It is not a restatement of the history.
Traps
- Calling a culturally sanctioned belief a delusion.
- Confusing flight of ideas (manic, with preserved link) with loosening of associations (schizophrenic).
- Describing negative symptoms (avolition, blunted affect) as depression without considering the longitudinal course.
- Failing to distinguish bizarre from non-bizarre delusions.
Worked example
A patient says his thoughts are being removed and replaced by a broadcaster. This is a passivity phenomenon / thought alienation, strongly suggesting schizophrenia - not an overvalued idea.