Abstracts

Rationale: Marijuana (cannabis) is one of the most commonly consumed illegal social drugs in Canada. The prevalence of past-year cannabis use among Canadians 15 years of age and older is 10.7% according to Health Canada. Nova Scotia's rate of consumption is 13.2%, statistically significantly higher than the national average. There is a paucity of valid clinical and experimental information available in regards to the role of cannabis in preventing or promoting seizures and its impact on seizure threshold. According to a review of the literature describing the effects of marijuana on epileptic symptoms in humans, cannabis use can reduce seizure frequency in some cases, provoke seizures in others, but in the majority of cases it probably has no effect. No one has systematically examined the role of regular cannabis use in persons presenting with first seizure. Methods: In our Adult First Seizure Clinic (FSC) at the QEII Health Sciences Centre, Halifax, N.S. we looked at self reported cannabis use in all patients referred for suspected first seizure. All patients who were assessed in the First Seizure Clinic were asked about consumption of marijuana. 395 new patients were assessed between May 2008 and June 2012. This information was then correlated with initial diagnosis; specifically First Seizure (FS), New Onset Epilepsy (NOE), Newly Diagnosed Epilepsy (NDE) or Other (O) diagnosis. NOE was defined as evidence of a preceding seizure(s) within 12 months of the index seizure. NDE was defined as evidence of a preceding seizure(s) beyond one year from the index seizure. Further information was collected in regards to age, gender, level of education, and employment status. We further analyzed marijuana usage in regards to occasional, regular, and heavy use. As part of our detailed assessment and counselling, we considered any other potentially provoking or triggering factors. Results: 170 patients were excluded from the data set for diagnosis other than FS, NDE or NOE. The remaining 228 patients were analyzed. None of these were felt to have experienced an acutely provoked seizure, according to ILAE criteria, as a result of either acute withdrawal or excessive use of marijuana. 112 were diagnosed with FS, 87 with NOE, and 26 with NDE. We found that 25.4% (58) of patients reported regularly using marijuana. 24.1% (27 patients) of those with FS, 31.0% (87 patients) with NOE and 34.6% (9 patients) with NDE reported regular use of marijuana. Conclusions: Our approach, which has been entirely epidemiological and descriptive at this stage, shows that self reported cannabis use in the Halifax First Seizure Clinic population is 25.4%; significantly more frequent than the 13.2% use reported in the general population for Nova Scotia. The numbers were similar regardless of initial diagnosis (FS, NOE, NDE). The population referred to the Halifax First Seizure Clinic reported unusually high regular use of marijuana. It is unclear exactly what role regular cannabis use has in this population in regards to impacting the individual seizure threshold.