Marijuana use by patients with multiple sclerosis

Background: With social attitudes about marijuana changing and patients sometimes seeking nonmainstream treatment options, the main goal of this study was to investigate the prevalence of, and factors associated with, marijuana use by patients with multiple sclerosis (MS). Methods: Adult patients with MS (n = 521) and controls (n = 279) from a study of clinical, neuroimaging, genetic, and environmental factors in MS progression were included. Patients with MS stated whether they had ever used marijuana before MS diagnosis, after MS diagnosis, and in the preceding 3 months as part of an in-person questionnaire. The control group stated whether they had ever used marijuana and in the preceding 3 months. Results: The percentage of patients with MS reporting ever use of marijuana was 39.9%, compared with 32.7% of controls. Marijuana use in the preceding 3 months was significantly more prevalent among patients with MS (9.4%) compared with controls (0.4%) (P < .001). Marijuana use was most prevalent in male patients with MS (P = .004) and in patients with MS who used complementary and alternative medicine (P = .045). Cigarette smoking was associated with marijuana use in patients with MS (P < .001) and controls (P = .001). Increasing age was associated with decreasing prevalence of marijuana use in the patients with MS (P < 0.001). Conclusions: Patients with MS are more likely to report recent marijuana use than are people without MS. Owing to potential adverse effects, marijuana use by patients with MS may warrant vigilance by MS caregivers, given shifting social attitudes and the trend towards legalization of marijuana in the United States.