Cognitive Mechanisms of Change in Delusions: An Experimental Investigation Targeting Reasoning to Effect Change in Paranoia

Philippa Garety, Helen Waller, Richard Emsley, Suzanne Jolley, Elizabeth Kuipers, P Bebbington, Graham Dunn, David Fowler, Amy Hardy, Daniel Freeman

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96 Citations (Scopus)
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Given the evidence that reasoning biases contribute to delusional persistence and change, several research groups have made systematic efforts to modify them. The current experiment tested the hypothesis that targeting reasoning biases would result in change in delusions.

One hundred and one participants with current delusions and schizophrenia-spectrum psychosis were randomly allocated to a brief computerised reasoning training intervention or to a control condition involving computer-based activities of similar duration. The primary hypotheses tested were that the reasoning training intervention, would improve i) data gathering and belief flexibility and ii) delusional thinking, specifically paranoia. We then tested whether the changes in paranoia were mediated by changes in data gathering and flexibility, and whether working memory and negative symptoms moderated any intervention effects.

On an intention-to-treat analysis, there were significant improvements in state paranoia and reasoning in the experimental compared to the control condition. There was evidence that changes in reasoning mediated changes in paranoia, although this effect fell just outside the conventional level of significance after adjustment for baseline confounders. Working memory and negative symptoms significantly moderated the effects of the intervention on reasoning.

The study demonstrated the effectiveness of a brief reasoning intervention in improving both reasoning processes and paranoia. It thereby provides proof-of-concept evidence that reasoning is a promising intermediary target in interventions to ameliorate delusions, and thus supports the value of developing this approach as a longer therapeutic intervention.
Original languageEnglish
Pages (from-to)400-410
Number of pages11
JournalSchizophrenia Bulletin
Issue number2
Early online date22 Jul 2014
Publication statusPublished - 1 Mar 2015


  • jumping to conclusions
  • belief flexibility
  • mediators
  • reasoning biases
  • Psychosis


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