Abstract

I have worked with people diagnosed with schizophrenia and psychosis for more than 25 years, and since 2012 I have led the treatment-resistant schizophrenia programme in Cambridge. Yet a decade ago I began to notice a striking shift in the clinical work. Increasingly, my time in the clozapine clinic was spent addressing intrusive thoughts and excessive checking rather than hallucinations or delusions. I began to screen every patient systematically. To my surprise, more than a third met criteria for obsessive–compulsive disorder. How could a hallucinatory–delusional syndrome evolve into what looked like a textbook OCD case? In this talk, I will present the work that followed this observation: epidemiological studies showing the scale and pattern of clozapine-related obsessive–compulsive symptoms; multilevel clinical models demonstrating how psychosis, depression, and clozapine dose interact to transform the psychopathology; and cognitive experiments revealing a distinctive form of dysfunctional checking that differs from both classical OCD and schizophrenia without OCS . These findings, developed in collaboration with Professor Trevor Robbins and colleagues, might represent an opportunity to bring cognitive neuroscience into clinical practice. I will close by outlining the conceptual implications and the future research aimed at understanding this transition and improving clinical care for patients.