Estimating the prevalence of schizophrenia amongst New Zealand Maori: a capture-recapture approach

Objective: The aim of the present study was to estimate the 12 month prevalence of schizophrenia in the Maori population of New Zealand. Method: Mental health data from two national sources were obtained for the period 2000-2003. A simple count of unique individuals with schizophrenia was used to estimate contact prevalence and a four-list capture-recapture procedure to estimate population prevalence. Results: Contact prevalence was significantly lower than the estimated population prevalence for both groups. The estimated 12 month prevalence of schizophrenia for Maori (0.97%) was significantly higher than for non-Maori (0.32%), even after adjustment for age, case under-ascertainment, and socioeconomic deprivation. Conclusions: The prevalence of schizophrenia among Maori appears to be elevated, although limitations in diagnostic reliability and recording of ethnicity must be considered. This adds further evidence of worldwide variation in the prevalence of schizophrenia. Capture-recapture provides a reliable cost-effective alternative to epidemiological surveys for estimating the prevalence of low-prevalence disorders such as schizophrenia.