Review provides nuanced assessment of CBD for epilepsy: modest benefits, notable drug interactions, and a gap between evidence and public belief | Research

The takeaway

While purified CBD shows modest but significant seizure improvement in Dravet and Lennox-Gastaut syndromes, important drug interactions (especially with clobazam and valproate) and a gulf between evidence and public expectations complicate the picture.

Epilepsy patients and families, neurologists, cannabis policy researchers

Up to 1 in 23 patients experience serious adverse events; significant interactions with clobazam and valproate

What the researchers found

Only purified CBD formulations have been rigorously evaluated in controlled trials, showing modest but significant improvements in motor seizures. Key adverse effects include diarrhea, somnolence, and reduced appetite, with up to 1 in 23 risk of serious adverse events. Significant drug interactions: valproate increases hepatotoxicity risk; clobazam interaction contributes to somnolence and potentially efficacy.

Why it matters

There is significant public enthusiasm for cannabis-based treatments for epilepsy that outpaces the actual evidence. This review helps calibrate expectations while acknowledging genuine therapeutic value.

The numbers in context

Up to 1 in 23 risk of serious adverse events from CBD. Drug interactions with valproate (hepatotoxicity) and clobazam (somnolence, efficacy). Only purified CBD has been rigorously tested in controlled trials.

How the study worked

Review summarizing current knowledge of cannabinoids for epilepsy, including controlled trial data for purified CBD, animal model evidence, drug interactions, and the gap between evidence and public perception.

What this study cannot tell us

No comparative effectiveness studies between CBD and other antiseizure medications; unclear how much of CBD's benefit is from direct anticonvulsant effect vs. clobazam interaction; limited evidence for THC-containing products.

How to read the evidence

Review synthesizing controlled trial evidence with clinical context and drug interaction data.

When this study was published

Published in 2020.

The bigger picture

The gap between public expectations (fueled by media and anecdote) and the actual evidence base for cannabinoids in epilepsy is a significant challenge for clinicians and policymakers.

Questions still open

How much of CBD's seizure benefit comes from its interaction with clobazam rather than direct anticonvulsant effects? Should THC-containing products be studied for epilepsy despite mental health risks?

Common questions

How effective is CBD for epilepsy?

Purified CBD has shown modest but statistically significant improvements in motor seizures in rigorous controlled trials for Dravet and Lennox-Gastaut syndromes. "Modest" means the effect is real but not dramatic for most patients.

What are the main safety concerns?

Key concerns include drug interactions with valproate (increased liver toxicity risk) and clobazam (increased somnolence), diarrhea, and up to a 1-in-23 chance of serious adverse events. The clobazam interaction also complicates understanding of whether CBD works directly or through altering clobazam levels.

Read the original research

A perspective on cannabinoids for treating epilepsy: Do they really change the landscape?

Neuropharmacology, 170, 107861

View on PubMed ↗Publisher’s paper ↗

Citation

Cross, J Helen; Cock, Hannah. (2020). A perspective on cannabinoids for treating epilepsy: Do they really change the landscape?. Neuropharmacology, 170, 107861. https://doi.org/10.1016/j.neuropharm.2019.107861