a1 Division of Psychiatry, School of Community Health Sciences, University of Nottingham, A Floor, South Block, Queen's Medical Centre, Nottingham, UK
a2 Department of Clinical Psychology, University of Sheffield, Sheffield, UK
a3 Section of Old Age Psychiatry, Institute of Psychiatry, King's College London, DeCrespigny Park, London, UK
a4 Department of Clinical Psychology, University of Liverpool, Liverpool, UK
a5 School of Psychological Sciences, University of Manchester, Oxford Road, Manchester, UK
a6 School of Psychology, University of Wales Bangor, Bangor, Gwynedd, UK
Background A tendency to make hasty decisions on probabilistic reasoning tasks and a difficulty attributing mental states to others are key cognitive features of persecutory delusions (PDs) in the context of schizophrenia. This study examines whether these same psychological anomalies characterize PDs when they present in the context of psychotic depression.
Method Performance on measures of probabilistic reasoning and theory of mind (ToM) was examined in five subgroups differing in diagnostic category and current illness status.
Results The tendency to draw hasty decisions in probabilistic settings and poor ToM tested using story format feature in PDs irrespective of diagnosis. Furthermore, performance on the ToM story task correlated with the degree of distress caused by and preoccupation with the current PDs in the currently deluded groups. By contrast, performance on the non-verbal ToM task appears to be more sensitive to diagnosis, as patients with schizophrenia spectrum disorders perform worse on this task than those with depression irrespective of the presence of PDs.
Conclusions The psychological anomalies associated with PDs examined here are transdiagnostic but different measures of ToM may be more or less sensitive to indices of severity of the PDs, diagnosis and trait- or state-related cognitive effects.
(Received March 14 2007)
(Revised September 27 2007)
(Accepted October 11 2007)
(Online publication November 16 2007)
c1 Address for correspondence: R. Corcoran, Ph.D., Division of Psychiatry, School of Community Health Sciences, University of Nottingham, A Floor, South Block, Queen's Medical Centre, Nottingham NG7 2UH, UK. (Email: firstname.lastname@example.org)