Method
Participants
One hundred and thirty patients with delusions from clinical services took part. The inclusion criteria were the following: age, 18–65; International Statistical Classification of Diseases-10 diagnosis of nonaffective psychosis (F20–F29); and a current delusion (rated ≥2 on the Schedules for Clinical Assessment in Neuropsychiatry),35 present for at least the last 3 months and held with at least 50% conviction. The exclusion criteria were a primary diagnosis of alcohol or drug dependency, organic brain disorder, diagnosed learning disability, or a command of English insufficient to complete assessments. The patients were recruited from 6 different National Health Service (NHS) sites in United Kingdom: South London and Maudsley NHS Foundation Trust, Norfolk and Waveney Mental Health NHS Foundation Trust, Camden and Islington NHS Foundation Trust, North East London NHS Foundation Trust, Barnet, Enfield and Haringey Mental Health NHS Trust, and Central and North West London NHS Foundation Trust