||Saha, S., Chant, D., Welham, J., & McGrath, J. (2005). A systematic review of the prevalence of schizophrenia. PLoS Medicine 2(5): e141. doi:10.1371/journal.pmed.0020141
||Background: Understanding the prevalence of schizophrenia has important implications for both health service planning and risk factor epidemiology.
Objectives: To systematically identify and collate studies describing the prevalence of schizophrenia, to summarize the findings of these studies, and to explore selected factors that may influence prevalence estimates.
Search strategy: Studies with original data related to the prevalence of schizophrenia (published 1965–2002) were identified via searching electronic databases (MEDLINE, PsycINFO, EMBASE, and LILACS), reviewing citations, and writing to authors.
Data collection and analysis: These studies were divided into “core” studies, “migrant” studies, and studies based on “other special groups.” Between and within study filters were applied in order to identify discrete prevalence estimates. Cumulative plots of prevalence estimates were made and the distributions described when the underlying estimates were sorted according to prevalence type (point, period, lifetime, and lifetime morbid risk). Based on combined prevalence estimates, the influence of selected key variables was examined (sex, urbanicity, migrant status, country economic index, and study quality).
Main results: A total of 1,721 prevalence estimates from 188 studies were identified. These estimates were drawn from 46 countries, and were based on an estimated 154,140 potentially overlapping prevalent cases. The authors identified 132 core studies, 15 migrant studies, and 41 studies based on other special groups. Based on combined prevalence estimates, the authors report no significant difference (a) between males and females, or (b) between urban, rural, and mixed sites. The prevalence of schizophrenia in migrants was higher compared to native-born individuals. Prevalence estimates from “least developed” countries were significantly lower than those from both “emerging” and “developed” sites.
Conclusions: There is a wealth of data about the prevalence of schizophrenia. These gradients, and the variability found in prevalence estimate distributions, can provide direction for future hypothesis-driven research.