Participants
Individuals with current delusions and a schizophreniaspectrum
disorder were recruited from mental health
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services within an UK National Health Service Trust
serving a population of approximately one million inhabitants,
the South London and Maudsley NHS Foundation
Trust. Inclusion criteria were a case note diagnosis
of schizophrenia or schizoaffective or delusional disorder,
a current delusional belief held with at least 75% selfrated
conviction, aged 18–65 years, and fluent in English.
Individuals were excluded if they had primary diagnosis
of alcohol or substance dependence, organic syndrome
or learning disability, or a profound visual impairment.
Thirty-nine individuals meeting the criteria were referred
for the study. Four individuals declined to take part, and
one individual was excluded because of clinical concerns.
Nonclinical participants were matched on age, ethnicity,
and occupation with the clinical group. They were
recruited from a locally developed database containing
the names of people from the general population who
were willing to take part in research. In addition, participants
were recruited from temporary staff working in the
South London and Maudsley NHS Foundation Trust
and by ‘‘snowball’’ sampling. Individuals were excluded
from the nonclinical group if they had a primary diagnosis
of organic syndrome, learning disability, profound visual
impairment, or nonfluent English or if they reported any
history of severe mental illness.