Joint effect of depression and chronic conditions on disability: Results from a population-based study

Objectives: To estimate and compare the prevalence of functional disability in individuals with both chronic medical conditions and comorbid major depression and individuals with either chronic medical conditions or major depression alone and to determine the joint effect of depression and chronic conditions on functional disability. Evidence exists that major depression interacts with physical illness to amplify the functional disability associated with many medical conditions. Methods: We used data from the Canadian Community and Health Survey Cycle 2.1 (n = 46,262), a nationally representative survey conducted in 2003 by Statistics Canada. Depression, chronic conditions, and functional disability were assessed by personal/telephone interview. Results: Prevalence of functional disability was higher in subjects with chronic conditions and comorbid major depression (46.3%) than in individuals with either chronic conditions (20.9%) or major depression (27.8%) alone. With no chronic conditions and no major depression as reference and after adjusting for relevant covariates, the odds ratio of functional disability was 2.49 (95% confidence interval (CI), 1.91-3.26) for major depression, 2.12 (95% CI, 1.93-2.32) for chronic conditions, and 6.34 (95% CI, 5.35-7.51) for chronic conditions and comorbid major depression. Conclusions: The results suggest that there is a joint effect of depression and chronic conditions on functional disability. Research and social policies should focus on the treatment of depression in chronic conditions.