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Delusion formation and reasoning biases in those at clinical high risk for psychosis

Section of Neuroimaging, Division of Psychological Medicine, Institute of Psychiatry, London, UK and Health Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry, UK

L. C. JOHNS, DPhil, DClinPsy, I. VALLI, MD, J. B. WOOLLEY, MRCP, MRCPsych, P. TABRAHAM, DClinPsy and C. BRETT, PhD, OASIS

Section of Neuroimaging, Division of Psychological Medicine, Institute of Psychiatry, London, UK

L. VALMAGGIA, PhD, DClinPsy, OASIS

Section of Neuroimaging, Division of Psychological Medicine, Institute of Psychiatry, London, UK and Department of Psychiatry and Neuropsychology, Maastricht University, The Netherlands

E. PETERS, PhD, DClinPsy and P. A. GARETY, PhD, FBPsS

Department of Psychology, Institute of Psychiatry, London, UK

P. K. McGUIRE, PhD, FRCPsych, OASIS

Section of Neuroimaging, Division of Psychological Medicine, Institute of Psychiatry, London, UK

Correspondence: Dr Matthew Broome, Health Sciences Research Institute, Warwick Medical School, University of Warwick, Coventry CV4 7A1, UK. Email: m.broome{at}iop.kcl.ac.uk

Declaration of interest None. Funding detailed in Acknowledgements.

Background Cognitive models propose that faulty appraisal of anomalous experiences is critical in developing psychosis, particularly delusions. A data gathering bias may be fundamental to abnormal appraisal.

Aims To examine whether there is a data gathering bias in people at high risk of developing psychosis.

Method Individuals with an at-risk mental state (n=35) were compared with a matched group of healthy volunteers (n=23). Participants were tested using a modified version of the ‘beads’ reasoning task with different levels of task difficulty.

Results When task demands were high, the at-risk group made judgements on the basis of less information than the control group (P<0.05). Within both groups, jumping to conclusions was directly correlated with the severity of abnormal beliefs and intolerance of uncertainty (P<0.05). In the at-risk group it was also associated with impaired working memory (P<0.05), whereas in the control group poor working memory was associated with a more conservative response style (P<0.05).

Conclusions People with an at-risk mental state display a jumping to conclusions reasoning style, associated with impaired working memory and intolerance of uncertainty. This may underlie a tendency to develop abnormal beliefs and a vulnerability to psychosis.