Cognitive approaches to delusions: A critical review of theories and evidence

Purpose. To review critically the evidence for three contemporary theories of delusions. Methods.The theoretical approachesto delusions proposedby Frith and colleagues ( ` theory of mind ’ de®cits), Garety and colleagues (multi-factorial, but involving probabilistic reasoning biases) and Bentall and colleagues (attributional style and self-discrepancies) are summarised. The ®ndings of empirical papers directly relevant to these proposals are critically reviewed. These papers were identi®ed by computerised literature searches (for the years 1987±1997) and a hand search. Results. The evidence does not unequivocally support any of the approaches as proposed. However, strong evidence is found to support modi®cations of Garety and colleagues ’ and Bentall and colleagues ’ theories. Studies have replicated a ` jumping to conclusions ’ data-gathering bias and an externalising attributional bias in people with delusions. There is preliminary evidence for a ` theory of mind’ de®cit, as proposed by Frith, although possibly related to a more general reasoning bias. Evidence for an underlying discrepancy between ideal and actual self