Delusions and belief flexibility in psychosis

A defining characteristic of delusions is inflexibility. However, it is not known if this is specific to the deluded individual's thinking about delusional beliefs, or whether this might apply more generally to the thinking style of people with delusions.

A cross-sectional design was employed comparing belief flexibility, belief dimensions, and extreme responding (ER) across three groups.

Belief flexibility and dimensions were assessed for two types of beliefs, personally meaningful beliefs (delusional or idiosyncratic beliefs) and standard beliefs. The number of extreme responses endorsed on a questionnaire was also measured. Participants consisted of a currently deluded group (N=17), a remitted delusions group (N=17), both recruited from an early psychosis service, and a non-clinical control group (N=35).

Personally meaningful beliefs, whether delusions or other idiosyncratic beliefs, were held with equal conviction and belief flexibility in the three groups. However, on the standard belief, the clinical groups showed less belief flexibility than the control group (with only the remitted group significantly so) and greater ER. Individuals who showed belief flexibility about both types of beliefs displayed less ER than those who were inflexible, and belief flexibility was related to less delusional conviction in the clinical groups.

These results suggest that belief inflexibility and ER may be characteristics of the thinking styles of individuals with delusions, rather than being specific to the delusional beliefs themselves. This has implications for cognitive behavioural therapy, which might usefully focus on generally thinking style as a preparation for working more directly with delusional beliefs.