Patients’ perceived benefit and side effects from the use of medicinal cannabis – a cross-sectional survey study from Denmark

Objectives Medicinal cannabis (MC) has recently been legalized in a growing number of countries. While MC is considered a potentially safe alternative or add-on to conventional treatments for pain, spasms, neuropathy, and chemotherapy-induced nausea/vomiting, evidence of its effectiveness and safety remains limited. This study aimed to assess patients’ perceived benefits and side effects of MC and explore patterns in side effect experiences. Methods We conducted a Danish nationwide online survey in 2020 among two groups of MC users: one with predefined diagnostic indications (neuropathic pain, chemotherapy-induced nausea/vomiting, or painful spasms from multiple sclerosis/paraplegia) (n=258) and one with other indications (n=786). Perceived benefit and side effects were measured using self-reported responses. We compared perceived benefit to the number of side effects and used a heat plot correlation matrix and exploratory factor analysis to identify patterns. Predicted factor scores were used to compare perceived benefit relative to side effect profiles, stratified by indication group. Results Most patients (67 %) reported a moderate to large effect of MC. Over half experienced side effects, with more than 10 % reporting three or more. Side effects were equally common among patients reporting a moderate to large vs. no to minor effect (p=0.27 and 0.68 for predefined and other indications). Side effects clustered into four groups: cognitive dysfunction, dizziness, xerostomia, and feeling “high.” These were not related to perceived benefit. Conclusions Most patients reported a moderate to large effect from MC. Over one in ten experienced three or more side effects, which were unrelated to perceived treatment effect.