Psychotic and psychotic-like experiences (PLEs) are frequently found in the general population when assessed with self-report questionnaires. It is not clear how these assessments can help to predict the future development of mental disorders. The degree of certainty in appraisal or the experience-related distress may add prognostic power of clinical PLE assessments. This study was designed to provide baseline data of PLEs in a representative sample, which will be monitored for the future development.
We studied the frequency of PLEs in a representative sample of 4483 participants of the German population recruited through the Mental Health Module of the German Health Interview and Examination Survey for Adults (DEGS1-MH). Participants were asked if they had had psychotic or psychosis-like experiences over their lifetime. We used the psychosis section of the Composite International Diagnostic Interview (CIDI), the Launay-Slade Hallucination Scale (LSHS) and the Peter's Delusion Inventory (PDI).
33.3% of the participants endorsed at least one item of the CIDI psychosis scale, 68.8% of the PDI and 49.0% of the LSHS. In the PDI assessments, conspiracy-related delusional experiences were most often experienced as distressing, while religious beliefs were experienced less distressing, but with high levels of conviction.
Our findings show frequent endorsement of lifetime psychotic or psychotic-like experiences in the general population in self-report questionnaires with varying degrees of distress and conviction. This provides the needed baseline assessment for follow-up studies observing the development of mental disorders with a view to determine the predictive values of these tests.