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      An evaluation of variation in published estimates of schizophrenia prevalence from 1990─2013: a systematic literature review

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          Abstract

          Background

          There is a lack of consistency in findings across studies on the prevalence of schizophrenia, and no recent systematic review of the literature exists. The purpose of this study is to provide an updated systematic review of population-based prevalence estimates and to understand the factors that could account for this variation in prevalence estimates.

          Methods

          MEDLINE, Embase, and PsycInfo databases were searched for observational studies describing schizophrenia prevalence in general populations from 2003–2013 and supplemented by studies from a prior review covering 1990–2002. Studies reporting prevalence estimates from specialized populations such as institutionalized, homeless, or incarcerated persons were excluded. Prevalence estimates were compared both across and within studies by factors that might contribute to variability using descriptive statistics.

          Results

          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.

          Conclusions

          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.

          Electronic supplementary material

          The online version of this article (doi:10.1186/s12888-015-0578-7) contains supplementary material, which is available to authorized users.

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          Most cited references95

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          Schizophrenia: a concise overview of incidence, prevalence, and mortality.

          Recent systematic reviews have encouraged the psychiatric research community to reevaluate the contours of schizophrenia epidemiology. This paper provides a concise overview of three related systematic reviews on the incidence, prevalence, and mortality associated with schizophrenia. The reviews shared key methodological features regarding search strategies, analysis of the distribution of the frequency estimates, and exploration of the influence of key variables (sex, migrant status, urbanicity, secular trend, economic status, and latitude). Contrary to previous interpretations, the incidence of schizophrenia shows prominent variation between sites. The median incidence of schizophrenia was 15.2/100,000 persons, and the central 80% of estimates varied over a fivefold range (7.7-43.0/100,000). The rate ratio for males:females was 1.4:1. Prevalence estimates also show prominent variation. The median lifetime morbid risk for schizophrenia was 7.2/1,000 persons. On the basis of the standardized mortality ratio, people with schizophrenia have a two- to threefold increased risk of dying (median standardized mortality ratio = 2.6 for all-cause mortality), and this differential gap in mortality has increased over recent decades. Compared with native-born individuals, migrants have an increased incidence and prevalence of schizophrenia. Exposures related to urbanicity, economic status, and latitude are also associated with various frequency measures. In conclusion, the epidemiology of schizophrenia is characterized by prominent variability and gradients that can help guide future research.
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            Systematic reviews: synthesis of best evidence for clinical decisions.

            Systematic reviews can help practitioners keep abreast of the medical literature by summarizing large bodies of evidence and helping to explain differences among studies on the same question. A systematic review involves the application of scientific strategies, in ways that limit bias, to the assembly, critical appraisal, and synthesis of all relevant studies that address a specific clinical question. A meta-analysis is a type of systematic review that uses statistical methods to combine and summarize the results of several primary studies. Because the review process itself (like any other type of research) is subject to bias, a useful review requires clear reporting of information obtained using rigorous methods. Used increasingly to inform medical decision making, plan future research agendas, and establish clinical policy, systematic reviews may strengthen the link between best research evidence and optimal health care.
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              Prevalence of psychiatric disorder in the general population: results of The Netherlands Mental Health Survey and Incidence Study (NEMESIS).

              This article reports the initial results of a prospective study on the prevalence of psychiatric disorders in the Dutch population aged 18-64. The objectives and the design of the study are described elsewhere in this issue. A total of 7076 people were interviewed in person in 1996. The presence of the following disorders was determined by means of the CIDI: mood disorders, anxiety disorders, eating disorders, schizophrenia and other non-affective psychoses, and substance use disorders. Psychiatric disorders were found to be quite common. Some 41.2% of the adult population under 65 had experienced at least one DSM-III-R disorder in their lifetime, among them 23.3% within the preceding year. No gender differences were found in overall morbidity. Depression, anxiety, and alcohol abuse and dependence were most prevalent, and there was a high degree of comorbidity between them. The prevalence rate encountered for schizophrenia was lower (0.4% lifetime) than generally presumed. A comparison with findings from other countries is made. Relevant determinants of psychiatric morbidity were analysed.
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                Author and article information

                Contributors
                +1 781 960 0274 , jason.simeone@evidera.com
                alex.ward@evidera.com
                Philip.rotella@evidera.com
                jennamcollins@gmail.com
                ricarda.windisch@gmail.com
                Journal
                BMC Psychiatry
                BMC Psychiatry
                BMC Psychiatry
                BioMed Central (London )
                1471-244X
                12 August 2015
                12 August 2015
                2015
                : 15
                : 193
                Affiliations
                [ ]Evidera, 430 Bedford Street, Suite 300, Lexington, MA 02420 USA
                [ ]F. Hoffmann-La Roche Ltd, Basel, Switzerland
                Article
                578
                10.1186/s12888-015-0578-7
                4533792
                26263900
                af8dbae3-fbaf-4337-9520-40bf3129642a
                © Simeone et al. 2015

                Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 15 April 2015
                : 28 July 2015
                Categories
                Research Article
                Custom metadata
                © The Author(s) 2015

                Clinical Psychology & Psychiatry
                Clinical Psychology & Psychiatry

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