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A systematic review of the prevalence of schizophrenia. Sukanta Saha David Chant Joy Welham John McGrath.
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A systematic review of the prevalence of schizophrenia Sukanta Saha David ChantJoy WelhamJohn McGrath
Schizophrenia is comprised of groups of brain disorders characterized by symptoms such as hallucinations, delusions, disorganized communication, poor planning, reduced motivation, and blunted affect. While the incidence of the disorder is relatively low (median value 15.2 per 100,000 persons per year), the condition is a major contributor to the global burden of disease. The substantial burden of schizophrenia results from: a) its typical onset in early adulthood, and b) despite optimal treatment, about two thirds of affected individuals have persisting or fluctuating symptoms. Understanding the prevalence of schizophrenia has important implications for both health service planning and risk factor epidemiology.
Aims To systematically identify and collate studies of the prevalence of schizophrenia To summarize variation in time, place and person by examining the distribution of these estimates of prevalence To explore factors which may influence prevalence estimates
Outline • Types of prevalence • Research questions • Methods • Key results • Caveats and Conclusions
The prevalence of schizophrenia:Research questions • Different types of prevalence • Sex difference Males vs females • Migrant status Migrants vs native born • Urbanicity Urban born vs rural born • Developed vs developing countries • Quality of methods
Types of prevalence studies • Population-based groups ‘Core studies’ Inpatient-Census-Derived data • Population sub-groups • Migrant studies • Other special groups
Methods: systematic review • Electronic data search • Medline, PsychoInfo, Embase, LILAC • 1965-2002 inclusive • (schizo* OR psycho*) AND (incidence OR prevalence) • Review article bibliography • Wrote to authors Screen abstract and reviewed papers to cull irrelevant citations
Estimates and discrete data Non-overlapping Sex Male, Female Overlapping Examples: Age eg. all ages or age 15-54 Diagnosis eg. Catego S+ or SPO + clinical Site overlap eg. Denmark or Copenhagen Epoch overlap eg. 1990-92 or 1989-91
Data analysis: example cumulative distribution Rate per 1,000
Results (2) After review • 188 studies from 46 countries • 1,721 prevalence estimates • 154,140 potentially overlapping cases Types of studies • Core studies = 132 • Migrant studies = 15 • Other special groups = 41
Core Prevalence Studies Point prevalence
Core Prevalence Studies Period prevalence
Core Prevalence Studies Lifetime prevalence
Core Prevalence Studies Lifetime Morbid Risk
Core Prevalence Studies Unspecified
Core Prevalence Studies Inpatient census prevalence
Key findings Like incidence, the prevalence of schizophrenia is variable across sites/groups: -it ranges from 3-7 per 1,000 persons, depending on the type of prevalence estimate -is higher in migrants vs native born Also countries from the developing world have a lower prevalence of schizophrenia Unlike incidence, the prevalence of schizophrenia -does not vary between the sexes - but there issubstantial variation between sites • is not higher in urban versus rural settings
Discussion • Comparisons in systematic reviews should be planned, based on directional hypotheses & limited to a reasonable number • Systematic reviews are best suited to hypothesis-generation • Geographical boundaries are administrative
Conclusions Many people with schizophrenia have persistent symptoms It is estimated that even given the best interventions, 3/4 of the burden of schizophrenia would remain This demands additional applied and basic etiological research Paradoxes like the differences between incidence and prevalence in sex differences and urban-rural settings demand further research