This retrospective cohort study examined whether frequent cannabis use (≥20 days/month) was associated with epilepsy severity, clinical phenotype, and imaging characteristics in 64 adults with drug-resistant epilepsy admitted to a tertiary epilepsy monitoring unit (EMU), comparing 22 frequent users to 42 nonusers.
Frequent cannabis users had significantly shorter time from epilepsy onset to EMU admission (5.0 vs. 18.1 years, p=.004), higher prevalence of focal to bilateral tonic-clonic seizures (FBTCS; 90.9% vs. 57.1%, p=.04), greater annualized FBTCS frequency (3.00 vs. 1.32, p=.003), and higher antiseizure medication (ASM) burden (3.05 vs. 2.21 medications, p=.027); all frequent users had temporal lobe epilepsy.
Small sample size (n=64) limits statistical power and generalizability; cannabis use was based on self-report from electronic medical records rather than objective biomarker measures, introducing potential misclassification; as a retrospective design, causality cannot be established and confounding by indication or unmeasured variables is possible.
Clinicians should routinely screen for frequent cannabis use in patients with drug-resistant epilepsy, as it is associated with more severe seizure burden and greater medication requirements. Prospective studies with objective cannabis exposure measures are needed before drawing causal conclusions.
