Physical ill health, disability, dependence and depression: Results from the 2007 national survey of psychiatric morbidity among adults in England

Background: The relationship between physical ill health, disability, and depression is not straightforward. Both cross-sectional and longitudinal studies have clearly shown that medical illness and physical disability are strongly associated with depression. Objective: To test the hypothesis that disability is associated with an increased prevalence of depression irrespective of physical health problems and that this is proportionate to the severity of disability (measured in terms of the number of difficulties in daily activities and the degree of dependence on others). Methods: Using a random probability sample design, 7460 respondents were interviewed for the third national survey of psychiatric morbidity of adults in the private household population in England. Fieldwork was carried out throughout 2007. The prevalence of depression was established by the administration of the revised Clinical Interview Schedule (CIS-R), while disability was measured by reported difficulties in activities of daily living (ADL) and instrumental activities of daily living (IADL). Results: Disability was associated with depression even after adjustment for physical ill health. The number of ADL/IADL difficulties was directly related to the likelihood of respondents having depression. Dependence on others was not associated with depression once severity of disability had been accounted for. Conclusion: All ADL/IADL limitations are significantly associated with depression and there seems to be a cumulative effect irrespective of whether the limitation is in personal care or in instrumental activities such as mobility problems.