Association between the use of selective serotonin reuptake inhibitors and multiple sclerosis disability progression

Background Benefits of selective serotonin reuptake inhibitors (SSRIs) in modifying the multiple sclerosis (MS) disease course have been suggested, but their ability to delay disability progression remains unknown. We examined the association between SSRI exposure and MS disability progression. Methods A nested case–control study was conducted using the British Columbia (Canada) Multiple Sclerosis clinical data linked to health administrative data. The primary outcome was a sustained score of 6 (requires a cane to walk) on the Expanded Disability Status Scale (EDSS), and the secondary outcome was the onset of secondary progressive MS (SPMS, an advanced stage of MS). The cases were those who reached a study outcome and were matched with up to four randomly selected controls by sex, age, EDSS and calendar year at study entry using incidence density sampling. The associations between disability worsening and SSRI exposure were assessed with conditional logistic regression models, adjusted for confounders. Results A total of 3920 patients were included in the main analyses, of which 272 reached sustained EDSS 6 and 187 reached SPMS. SSRI exposure was significantly different between patients who reached sustained EDSS 6 and controls [adjusted odds ratio (adjOR):1.44; 95% confidence interval (CI):1.03–2.01]. However, SSRI exposure was not significantly different between those who reached SPMS and their controls (adjOR:1.35; 95%CI:0.89–2.04). Conclusion We found no evidence to suggest that SSRI exposure was associated with a delay in MS disability accumulation or progression.