Introduction A number of studies have shown that there is international variation in the prevalence of common mental disorders. Several factors have been suggested to explain such differences. Methodological challenges to comparability include: differences in settings, samples, assessment methods, and reporting practices. Also, cultural differences have been pointed out as possible cause of differential recognition and reporting of mental health issues. There is still uncertainty about the degree of international variation in the prevalence of mental disorders, and the lack of comparability of results is still an issue.
Objectives We assessed the prevalence and impact of mental disorders in the WHO World Mental Health (WMH) Survey Initiative, using common survey, assessment and reporting methods.
Methods The WMH surveys were completed in 24 countries from Africa, the Americas, Asia, Europe, the Middle-East and the Pacific. Representative samples of the adult, non-institutionalizes population were interviewed face-to-face, with the aim of estimating the prevalence, burden and unmet need for treatment of common mental disorders. The Composite International Diagnostic Interview (CIDI, 3.0) was used in all surveys to assess mental health status. Common mental disorders assessed included: anxiety, mood, disruptive behaviour, and substance disorders. Several standard measures of disability, both generic and disorder-specific, and role impairment were administered.
Results Results show that the mental disorders are commonly occurring in all participating countries. The inter-quartile range (IQR: 25th–75th percentiles) of lifetime DSM-IV disorder prevalence estimates (combining anxiety, mood, disruptive behaviour, and substance disorders) is 18.1–31.1%. The IQR of 12 month prevalence estimates is 9.8–19.1%. Prevalence estimates of 12-month Serious Mental Illness (SMI) are 4–6.8% in half of the countries, 2.3–3.6% in one-fourth and 0.8–1.9% in one-fourth. Possible causes of international variation will be addressed. Analysis of age-of-onset reports shows that many mental disorders begin in childhood-adolescence and have significant adverse effects on subsequent role transitions. Mental disorders are found in the WMH data to be associated with high levels of role impairment.
Conclusions Despite this burden, the majority of mental disorders go untreated. Although these results suggest that expansion of treatment could be cost-effective form both the employer perspective and the societal perspective, treatment effectiveness trials are needed to confirm this suspicion. The WMH results regarding impairments are being used to target several of these interventions.
Additional information about the WMH Surveys Initiative and the funing of the project can be found at: http://www.hcp.med.harvard.edu/wmh/