An Evaluation of Variation in Published Estimates of Schizophrenia Prevalence from 1990─2013: A Systematic Literature Review

Below:  Prevalence of Schizophrenia in North America, Europe, Australia, and New Zealand. Countries are designated by 3-letter International Organization for Standardization (ISO) code. CAN: Canada; USA: United States; DNK: Denmark; FIN: Finland; IS: Iceland; IRL: Ireland; ITA: Italy; NLD: Netherlands; ESP: Spain; SWE: Sweden; GBR: United Kingdom; DEU: Germany; AUS: Australia; NZL: New Zealand. *Former West Germany

Sixty-five primary studies were included; thirty-one (48 %) were from Europe and 35 (54 %) were conducted in samples of ≥50,000 persons. Among 21 studies reporting 12-month prevalence, the median estimate was 0.33 % with an interquartile range (IQR) of 0.26 %–0.51 %. The median estimate of lifetime prevalence among 29 studies was 0.48 % (IQR: 0.34 %–0.85 %). Prevalence across studies appeared to vary by study design, geographic region, time of assessment, and study quality scores; associations between study sample size and prevalence were not observed. Within studies, age-adjusted estimates were higher than crude estimates by 17 %–138 %, the use of a broader definition of schizophrenia spectrum disorders compared to schizophrenia increased case identification by 18 %–90 %, identification of cases from inpatient-only settings versus any setting decreased prevalence by 60 %, and no consistent trends were noted by differing diagnostic criteria.

This review provides updated information on the epidemiology of schizophrenia in general populations, which is vital information for many stakeholders. Study characteristics appear to play an important role in the variation between estimates. Overall, the evidence is still sparse; for many countries no new studies were identified.

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