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. 2005 May;2(5):e141.
doi: 10.1371/journal.pmed.0020141. Epub 2005 May 31.

A systematic review of the prevalence of schizophrenia

Sukanta Saha  1 , David Chant, Joy Welham, John McGrath
Affiliations

A systematic review of the prevalence of schizophrenia

Sukanta Saha et al. PLoS Med. 2005 May.

Abstract

Background: Understanding the prevalence of schizophrenia has important implications for both health service planning and risk factor epidemiology. The aims of this review are 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.

Methods and findings: Studies with original data related to the prevalence of schizophrenia (published 1965-2002) were identified via searching electronic databases, reviewing citations, and writing to authors. 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). 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. We identified 132 core studies, 15 migrant studies, and 41 studies based on other special groups. The median values per 1,000 persons (10%-90% quantiles) for the distributions for point, period, lifetime, and lifetime morbid risk were 4.6 (1.9-10.0), 3.3 (1.3-8.2), 4.0 (1.6-12.1), and 7.2 (3.1-27.1), respectively. Based on combined prevalence estimates, we found 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: the migrant-to-native-born ratio median (10%-90% quantile) was 1.8 (0.9-6.4). When sites were grouped by economic status, prevalence estimates from "least developed" countries were significantly lower than those from both "emerging" and "developed" sites (p = 0.04). Studies that scored higher on a quality score had significantly higher prevalence estimates (p = 0.02).

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.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Flow Diagram (Selection Strategy) of Included Studies
Double asterisk indicates exclusion categories (number studies excluded in parentheses). Double asterisk indicates numbers that are not mutually exclusive. A few studies provided rates for more than one group (11 studies provided data for both core and migrant [n = 3] or both core and other special groups [n = 8]; details in Results). LOTE, language other than English.
Figure 2
Figure 2. Cumulative Plots of the Point Prevalence Estimates per 1,000 by Sex
Figure 7
Figure 7. Cumulative Plots of the Inpatient-Census-Derived Prevalence Estimates per 1,000 by Sex
Figure 3
Figure 3. Cumulative Plots of the Period Prevalence Estimates per 1,000 by Sex
Figure 4
Figure 4. Cumulative Plots of the Lifetime Prevalence Estimates per 1,000 by Sex
Figure 5
Figure 5. Cumulative Plots of the LMR Estimates per 1,000 by Sex
Figure 6
Figure 6. Cumulative Plots of the NOS Prevalence Estimates per 1,000 by Sex
Figure 8
Figure 8. Cumulative Plots of Combined Prevalence Estimates per 1,000 by Sex
Figure 9
Figure 9. Cumulative Plots of the Male:Female Prevalence Estimate Ratio of Schizophrenia
Figure 10
Figure 10. Cumulative Plots of Combined Prevalence Estimates per 1,000 for Persons by Urbanicity
Figure 11
Figure 11. Cumulative Plots of the Migrant:Native-Born Prevalence Estimate Ratio for Persons
Figure 12
Figure 12. Cumulative Plots of the Combined Prevalence Estimates per 1,000 for Persons by Economic Status of Country
Figure 13
Figure 13. Cumulative Plots of the Male:Female Prevalence Estimate Ratio of Schizophrenia by Economic Status of Country
Figure 14
Figure 14. Cumulative Plots of Combined Prevalence Estimates per 1,000 for Persons by Tercile of Quality Score
See this image and copyright information in PMC

Comment in

  • The global prevalence of schizophrenia.
    Bhugra D. Bhugra D. PLoS Med. 2005 May;2(5):e151; quiz e175. doi: 10.1371/journal.pmed.0020151. Epub 2005 May 31. PLoS Med. 2005. PMID: 15916460 Free PMC article.
  • Secondary schizophrenia.
    Hambidge D. Hambidge D. PLoS Med. 2005 Sep;2(9):e279; author reply e300. doi: 10.1371/journal.pmed.0020279. Epub 2005 Sep 27. PLoS Med. 2005. PMID: 16173833 Free PMC article. No abstract available.

References

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