CBD May Not Have Anti-Seizure Properties On Its Own | Research

The takeaway

A rigorous placebo-controlled trial found that CBD at both low and high doses had no significant effect on cortical excitability or sedation in healthy men, suggesting its anti-epileptic benefits may come primarily from drug interactions with clobazam.

Neurologists prescribing CBD for epilepsy, pharmacologists studying cannabinoid mechanisms, epilepsy researchers, and patients interested in how CBD works.

What the researchers found

Single doses of 30 mg and 700 mg CBD had no significant effects on single-pulse or paired-pulse TMS-EMG measures of cortical excitability, nor on validated CNS sedation tests, compared to placebo — suggesting CBD may lack intrinsic anti-epileptic and sedative properties.

Why it matters

If CBD's approved anti-seizure effects are primarily driven by drug interactions with clobazam rather than direct anti-epileptic activity, it fundamentally changes how we understand and prescribe CBD for epilepsy.

The numbers in context

n=25 healthy males; 3-way crossover; 30 mg and 700 mg CBD vs. placebo; no significant effects on TMS-EMG; some TMS-EEG clusters at 3 and 5 hours post-dose for 700 mg; no effects on sedation battery

How the study worked

Randomized, double-blind, placebo-controlled, 3-way crossover trial in 25 healthy males testing single doses of 30 mg CBD, 700 mg CBD, and placebo using transcranial magnetic stimulation with EMG/EEG and a validated CNS test battery.

What this study cannot tell us

Healthy volunteers (not epilepsy patients); single-dose study doesn't capture chronic effects; males only; TMS measures may not fully capture anti-epileptic mechanisms; some TMS-EEG clusters were significant suggesting subtle effects.

How to read the evidence

Gold-standard RCT design (randomized, double-blind, placebo-controlled, crossover) with objective neurophysiological outcomes, though limited to healthy males and single dosing.

When this study was published

Published 2026; reflects current mechanistic understanding of CBD pharmacology.

The bigger picture

This challenges the widespread assumption that CBD is inherently anti-epileptic, suggesting its clinical benefits in Dravet and Lennox-Gastaut syndromes may depend on pharmacokinetic boosting of co-administered medications.

Questions still open

Would repeated dosing reveal different effects? Are there other anti-seizure mechanisms not captured by TMS? Does CBD have direct effects in diseased brain tissue that don't appear in healthy subjects?

Common questions

Does CBD directly prevent seizures?

This study suggests possibly not — CBD showed no effect on brain excitability measures at any dose in healthy volunteers, raising the possibility that its anti-seizure benefits come primarily from boosting the effects of other medications like clobazam.

How does CBD work for epilepsy if it doesn't directly affect brain excitability?

CBD inhibits the enzyme that breaks down clobazam (a common co-prescribed anti-seizure medication), effectively increasing clobazam levels in the blood — which may be the primary mechanism behind its epilepsy benefits.

Read the original research

Cannabidiol Lacks Direct Effect on Cortical Excitability: A Randomized, Double Blind, Placebo Controlled, 3-Way Crossover Trial.

Clinical pharmacology and therapeutics, 119(1), 147-157

View on PubMed ↗Publisher’s paper ↗

Citation

Gorbenko, Andriy A; de Cuba, Catherine M K E; de Goede, Annika A; Post, Titiaan E; Bohoslavsky, Roman; Strugala, Pamela K; Heuberger, Jules A A C; Groeneveld, Geert Jan. (2026). Cannabidiol Lacks Direct Effect on Cortical Excitability: A Randomized, Double Blind, Placebo Controlled, 3-Way Crossover Trial.. Clinical pharmacology and therapeutics, 119(1), 147-157. https://doi.org/10.1002/cpt.70038