Cognitive functioning in delusions: a longitudinal analysis

This study explored the longitudinal course of the relationship between delusions and different aspects of cognitive functioning.

Deluded patients were compared to psychiatric and non-clinical controls on three tasks: negative priming, a probabilistic judgement task (the 'beads' task), and the pragmatic inference task (PIT). All groups were tested at two time points, once when actively symptomatic, and once when in remission.

Deluded individuals exhibited a 'jump-to-conclusions' (JTC) reasoning bias: i.e., they made decisions on the basis of limited evidence and were more likely to revise their estimates when faced with disconfirmatory evidence. This JTC bias remained stable over time, although probability judgments seemed to normalise in remission. No deficits in cognitive inhibition were found on negative priming. The deluded group displayed an excessive self-focus on the PIT at both time points, but did not show a depressive attributional style. Only a small sub-sample, characterised by the "bad-me" type of paranoia [Trower & Chadwick, 1995 Clinical Psychology: Science and Practice, 2, 263-278.], demonstrated depressive schemas when symptomatic, but no longer did so when remitted. Few relationships were found between tasks, suggesting that different areas of functioning are relatively independent. The only measures associated with delusion symptom scores were from the 'beads' task.

Overall these findings suggest that the JTC bias is a stable factor associated with delusional thinking, while the depressive attributional style characteristic of a small sub-sample of paranoid patients fluctuates with delusional course.