Prevalence, incidence, and persistence of psychotic experiences in the general population: results of a 9-year follow-up study.

Background: Psychotic experiences (PEs) frequently occur and are associated with a range of negative health outcomes. Prospective studies on PEs are scarce, and to date no study investigated PE prevalence, incidence, persistence, their risk indicators, and psychiatric comorbidity, in one dataset. Furthermore, most studies are based on self-report, and it is unclear how this compares to clinical interviews.

Methods: Data are used from the Netherlands Mental Health Survey and Incidence Study-2 (NEMESIS-2), a psychiatric cohort study among a representative sample of adults (baseline characteristics: = 6646; 49.6% female; 18-64 years). Results are presented for self-reported and clinically validated PEs. Associations are assessed for mental disorders, socio-demographic, vulnerability, physical health, and substance use factors.

Results: Based on self-report, at baseline 16.5% of respondents had at least one PE in their lifetime, of those, 30.1% also reported a PE at 3-year follow-up. 4.8% had a first PE at 3-year follow up. The 3-year prevalence of PE was associated with almost all studied risk indicators. Generally, the strongest associations were found for mental health disorders. Prevalence and incidence rates were two to three times higher in self-report than in clinical interview but results on associated factors were similar.

Conclusions: Validated prevalence and incidence estimates of PE are substantially lower than self-reported figures but results on associated factors were similar. Therefore, future studies on associations of PEs can rely on relatively inexpensive self-reports of PEs. The associations between PE and mental disorders underline the importance of assessment of PE in general practice.