Incident depression in patients diagnosed with multiple sclerosis: a multi-database study.

BACKGROUND: Data on rates of newly diagnosed depression after multiple sclerosis (MS) diagnosis are sparse. Here, we describe incident, treated depression in MS patients after diagnosis compared with matched non-MS patients. METHODS: We conducted a matched cohort study in two separate electronic medical databases: United States Department of Defense (US-DOD) military health care system and United Kingdom's Clinical Practice Research Datalink GOLD (UK-CPRD). The study population included all patients with a first recorded diagnosis of MS and matched non-MS patients. Patients with a history of treated depression were excluded. We identified incident treated depression after the MS diagnosis / matched date and calculated incidence rates and incidence rate ratios (IRRs) with 95% confidence intervals (CI). RESULTS: IRRs of treated depression among MS patients compared with non-MS patients were IRR 3.20 (95% CI 3.05-3.35) in the US-DOD and 1.90 (95% CI 1.74-2.06) in the UK-CPRD. IRRs were elevated across age and sex. Rates were higher in females than males but compared to non-MS patients, males with MS had a higher relative risk than females with MS. CONCLUSIONS: MS patients in the UK and the US have 2- to 3- fold increased risk of new, treated depression compared to matched non-MS patients.