Nationwide Study of Postlegalization Marijuana Use Among Patients With Epilepsy in Canada

Patients with epilepsy have long sought alternatives to conventional antiseizure medications (ASMs) for the treatment of their epilepsy and to improve the significant side effect burden of ASMs and comorbidities. It was established before the legalization of marijuana in Canada in 2018 that many patients with epilepsy use marijuana to treat their seizures or for recreational purposes. However, there exists no current data on the prevalence and habits of marijuana use in the Canadian epilepsy population since legalization.

We conducted a nationwide cross-sectional survey of patients recruited through health care providers or epilepsy organizations to investigate marijuana usage habits and perceptions.

From 395 responses obtained through the survey, 221 responses stated that they used marijuana within the past year. A history of seizures for more than 10 years was noted in 50.7% (n = 148) patients with generalized seizures being the most common type (n = 169; 57.1%). Most of them (n = 154; 52.0%) had tried 3 or more ASMs, and 37.2% (n = 110) used various other treatments (ketogenic diet, vagus nerve stimulation, or resective surgery) indicating a proportion with drug-resistant epilepsy. This subgroup was more likely to have started using marijuana for drug-resistant epilepsy (p < 0.001). Current marijuana use for epilepsy management was endorsed by 47.5% (n = 116). Marijuana was "somewhat" to "very" effective at reducing seizure frequency for 60.1% (n = 123). The main side effects of marijuana were impaired thinking (n = 40; 17.17%), anxiety (n = 37; 15.74%), and altered hunger (n = 36; 15.32%). Marijuana was used at least once daily by 70.3% (n = 168) with the median amount per week being 5.0 g (IQR = 1-10), and the preferred method of consumption was smoking (n = 83; 34.7%). The participants expressed concerns regarding financial strain (n = 108; 36.5%), lack of recommendation from a doctor (n = 89; 30.1%), and lack of information (n = 56; 18.9%) surrounding marijuana use.

This study reveals a high prevalence of marijuana use among patients with epilepsy living in Canada particularly when seizures are drug resistant. A significant proportion of patients reported improvement of seizures with marijuana use, consistent with previous studies. With the increased accessibility of marijuana, it is imperative that physicians are aware of marijuana usage habits among patients with epilepsy.