Effects of Marijuana on ictal and interictal EEG activity in idiopathic generalized epilepsy.

Marijuana-based treatment for refractory epilepsy shows promise in surveys, case series and clinical trials. However, literature on their electroencephalography (EEG) effects is sparse. Our objective is to analyze the effect of marijuana on EEG in a 24-year-old patient with idiopathic generalized epilepsy (IGE) treated with cannabis. We blindly reviewed three long-term EEGs-a 24-hour study while only on antiepileptic drugs (AEDs), a 72-hour EEG with Cannabis indica smoked on days one and three in addition to AEDs and a 48-hour EEG with combination C. indica/sativa smoked on day one plus AEDs. Generalized spike-wave discharges and diffuse paroxysmal fast activity were categorized as interictal and ictal, based on duration of less than 10 seconds or greater, respectively. Data from three studies concatenated into contiguous time series, with usage of marijuana modeled as time dependent discrete variable while interictal and ictal events constituted dependent variables. ANOVA as initial test for significance followed by time-series analysis using Generalized Autoregressive Conditional Heteroscedasticity (GARCH) model was performed. Statistical significance for lower inter-ictal events (ANOVA p=0.001) was seen during C. indica use, but not for C.indica/sativa mixture (p=0.629) or ictal events (p=0.087). However, time-series analysis revealed a significant inverse correlation between marijuana use, with interictal (p<0.0004) and ictal (p=0.002) event rates. Using a novel approach to electroencephalographic data, we demonstrate a decrease in interictal and ictal electrographic events during marijuana use. Larger samples of patients and EEG, with standardized cannabinoid formulation and dosing are needed to validate our findings.