A patient has had several normal medical investigations but remains highly preoccupied with a feared serious illness. Which single question would best help clarify whether this is a delusion of ill health rather than ordinary health anxiety?
Directly testing how the person would respond to normal evidence — rather than assuming from distress level alone — is the most efficient way to establish fixity, the feature that actually separates a delusion of ill health from ordinary health anxiety. Symptom description, duration, and family history are useful clinical background but do not themselves distinguish a fixed, delusional conviction from a health worry that remains genuinely open to reassurance.
Key discriminating feature: The defining difference between a delusion of ill health and ordinary health anxiety is fixity — whether the belief can, even in principle, be shifted by clear objective evidence — so asking directly about this hypothetical is the most efficient way to test it.
Clinical interviewing principle: Test fixity directly rather than inferring it from how distressed or preoccupied the person seems, since severity of distress and fixity of belief are not the same thing and can be present independently of each other.
References
- Casey, P. & Kelly, B. (2019). Fish's Clinical Psychopathology, 4th ed. Ch. 4, 'Disorders of Thought and Speech'.