Madness Explained: Psychosis and Human Nature

by Richard P. Bentall

I am aware of only one study in which an attempt has been made to assess the prevalence of different kinds of delusions. In June 1996, thirty-one family doctors in the Aquitaine region of southwest France asked over 1000 patients attending their clinics to complete a questionnaire measuring twenty-one commonly reported delusional beliefs. Only 11.5 per cent of those approached had attended their doctor because of psychiatric problems. The most common delusional ideas reported were that people were not who they seemed to be (69.3 per cent of those with no history of psychiatric disorder); that the individual had experienced telepathic communication (46.9 per cent); that seemingly innocuous events had double meanings (42.2 per cent); that the individual was being persecuted in some way (25.5 per cent); and that occult forces were at work (23.4 per cent).