Using Population Health Surveys to Measure the Use of Services and the Prevalence of Psychiatric and/or Behavioural Conditions in Individuals with an Intellectual Disability
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Background: Compared to the general population, individuals with intellectual disabilities have a higher prevalence of health problems, including psychiatric and/or behavioural conditions (dual diagnosis). Research suggests that the proportion of persons with intellectual disabilities who have a dual diagnosis ranges from 14% to 64% depending on the population studied and the diagnostic criteria used. However, there is little population-based information in Canada about people with such a dual diagnosis. Objectives: The aims of this study were to estimate the prevalence of psychiatric or behavioural conditions among adults with an intellectual disability in Canada, and to estimate the use of mental health services among these individuals. Methods: This study was a secondary analysis of two cross-sectional, population-based surveys (2005 Canadian Community Health Survey: CCHS and 2006 Participation and Activity Limitation Survey: PALS), and the 2008/09 Survey of Adults with Intellectual Disabilities in South Eastern Ontario: SAID-SEO. Relevant variables were identified in the surveys to answer the study objectives. Confidence intervals were provided for all estimates and the results were compared within subgroups for each survey, as well as between surveys. Results: The proportion of Canadian adults with an intellectual disability is 0.2% according to the CCHS and 0.5% according to the PALS. The proportion of individuals with a dual diagnosis was found to be 31% in the CCHS, 44% in the PALS, and 33% in the SAID-SEO. These prevalence estimates fall within the ranges reported in the literature. Lastly, the majority of adults with a dual diagnosis reported using health services in the past year. Conclusion: According to the three surveys examined (CCHS, PALS, SAID-SEO), psychiatric and behavioural conditions are present in about a third of the individuals with intellectual disabilities, which is in accordance with published literature. However, the estimates of the prevalence of intellectual disabilities in the CCHS and PALS were considerably lower when compared to the literature. Among the surveys, the PALS presented the highest quality of data regarding the population with a dual diagnosis. The surveys found that a majority of individuals with a dual diagnosis access some form of health services at least once a year.