Diagnosis and treatment of depression following routine screening in patients with coronary heart disease or diabetes: a database cohort study

Background. Depression is common in chronic illness and screening for depression has been widely recommended. There have been no large studies of screening for depression in routine care for patients with chronic illness. Method. We performed a retrospective cohort study to examine the timing of new depression diagnosis or treatment in relation to annual screening for depression in patients with coronary heart disease (CHD) or diabetes. We examined a database derived from 1.3 million patients registered with general practices in Scotland for the year commencing 1 April 2007. Eligible patients had either CHD or diabetes, were screened for depression during the year and either received a new diagnosis of depression or commenced a new course of antidepressant (excluding those commonly used to treat diabetic neuropathy). Analysis was by the self-controlled case-series method with the outcome measure being the relative incidence (RI) in the period 1-28 days after screening compared to other times. Results. A total of 67358 patients were screened for depression and 2269 received a new diagnosis or commenced treatment. For the period after screening, the RI was 3.03 [95% confidence interval (CI) 2.44-3.78] for diagnosis and 1.78 (95% CI 1.54-2.05) for treatment. The number needed to screen was 976 (95% CI 886-1104) for a new diagnosis and 687 (95% CI 586-853) for new antidepressant treatment. Conclusions. Systematic screening for depression in patients with chronic disease in primary care results in a significant but small increase in new diagnosis and treatment in the following 4 weeks.