With a third of epilepsy patients not responding to conventional treatment, there is an understandable demand for novel or alternative therapies. Cannabis, whose properties in epilepsy have long been discussed, has recently returned to the spotlight. Preclinical and exploratory clinical studies have provided promising results in some forms of intractable epilepsy, but large sustained epidemiological evidence of its effects is still lacking.
A new step in this direction has been undertaken by Andreu Massot-Tárrus and Richard McLachlan from Western University in London, Ontario. During the course of a year, the authors administered a questionnaire to more than 300 patients admitted to an epilepsy monitoring unit, which included several questions about their clinical history, drug use, and its perceived effects.
Using EEG recordings, 292 patients were diagnosed as having epilepsy or having psychogenic nonepileptic seizures (PNES). Of these, 36% reported to have been using cannabis during the last year, with most having done so for 8 years straight. Half of these patients were daily users, and a fifth were weekly users. Pooled together, participants consumed on average 1 gram of cannabis per day, mostly via smoking, though more than a third had tried different methods.
The two groups were comparable in terms of ongoing cannabis use and duration of use, but epileptic patients were more likely to be daily users and to consume it with the intention of treating their condition. Overall, cannabis use was associated with being male, younger age, lower education, and tobacco, but not alcohol use.
Only a mere 6% of cannabis users obtained the drug through official medical marijuana prescriptions. This is in line with a previous study that uncovered a general dissatisfaction of epileptic patients regarding the quality of the products supplied by the government.
Of the 108 epileptic patients who consumed cannabis, 84% reported an overall improvement in seizure frequency and intensity, and about a fifth considered it to be “very effective”. These results were similar to those of PNES patients, which suggests that the effects might not be due to a direct regulation of the brain’s electrical activity, but to other factors.
In support of this idea, the authors found that the improvement in seizures in both groups was moderately correlated to the reduction in stress following cannabis use. Another factor that likely played a role was placebo, since the patients using cannabis with the goal of controlling seizures were much more likely to report improvements than those using it merely for recreational or other goals. Finally, other variables that were not controlled by the authors, such as tobacco intake, might also explain the effects observed.
According to the patients’ reports, symptoms such as sleep, antiepileptic drugs’ side effects, concentration, and memory also tended to improve with cannabis use. On a less positive note, nearly a third of patients reported mild side effects (while twice as many reported similar side effects from antiepileptic medication). More worrisome was the possibility of cannabis exacerbating seizures, as suggested by five epileptic patients.
The study offered preliminary epidemiological evidence that cannabis could be helpful in the management of adult intractable epilepsy as well as PNES, potentially via stress reduction. Several limitations, however, should be highlighted — namely, it being a retrospective study, being based on self reports, lacking a controlled quantification of symptoms or drug intake, not controlling for potential confounds, and employing a novel questionnaire that has not been validated by prior research.
Conflict of interests reported: during the study, Dr. McLachlan received honoraria from UCB Canada, Sunovion, and Eisai.