Diagnostic stability in a Dutch psychosis incidence cohort.

Background: No study outside the UK has examined the diagnostic stability of psychotic disorders in a population-based sample.

Aims: To determine diagnostic stability in a Dutch population-based psychosis incidence cohort, to examine the frequencies of diagnostic shifts to and from schizophrenic disorders and to report the revised relative risks of schizophrenic disorders for immigrants.

Method: A 30-month follow-up study assessed the cohort (n=181) by means of face-to-face diagnostic interviews.

Results: Diagnostic stability of schizophrenic disorders was high (91%), but lower for other psychotic disorders. At follow-up, the initial diagnosis was adjusted to schizophrenic disorder more often than that the reverse occurred. Almost half (49%) of the patients who were not initially diagnosed as having a schizophrenic disorder received this diagnosis at follow-up. The relative risks for most immigrant groups were stable.

Conclusions: Schizophrenic disorders are underdiagnosed, rather than overdiagnosed, at first presentation.