What is the relative importance of self reported psychotic symptoms in epidemiological studies? Results from the ESEMeD—Catalonia Study

Different prevalence of non-affective psychosis has been reported in general population surveys. The objectives of this study were to describe lifetime prevalence of non-affective psychosis in Catalonia, Spain; and to analyze the use of the CIDI psychosis module as a screening instrument for psychotic disorders. As part of the ESEMeD project in Catalonia, 1645 respondents were assessed with the CIDI. Respondents who scored positively to any of the CIDI psychosis screen questions, who had been hospitalised for a psychiatric reason or had received antipsychotic medication were re-assessed with the SCID-I by a clinician. The results showed that 11.18% people of the sample had lifetime self reported psychotic symptoms using the CIDI. After a clinical interview with the SCID-I, between 0.85 and 2.37% of the sample had a psychotic disorder, and 0.48%–1.58% had schizophrenia. The most frequent reported psychotic symptoms in individuals without a psychotic disorder were those related with hearing or seeing something missing during a bereavement period. Experiencing mind control, feeling that your mind was being controlled by strange forces, experiencing attempts of communications (CIDI questions) and taking medication were the items that discriminate between non-affective psychosis cases and negatives. Only experiencing mind control was associated with psychotic disorders in a logistic regression analysis. The main conclusions are that the use of lay-administered interviews should only be used as a screening instrument in the detection of psychosis in general population surveys because the majority of self reported psychotic symptoms have not been found to be associated with a psychotic disorder.