Published summary: 2026-03-07
Where the evidence converges
Meta-analysis of 550 patients found CBD reduced seizures by ~20 percentage points in severe childhood epilepsies
Strong evidence · 10 studies
Only four trials available, all in LGS and DS specifically. Results may not generalize to other epilepsy types. All trials used pharmaceutical-grade CBD (Epidiolex), so findings do not apply to unregu
Meta-analysis of pivotal trials found CBD has independent anti-seizure effects, though the benefit is amplified by interaction with clobazam
Strong evidence · 10 studies
Subgroup analyses were not pre-specified. Small numbers in non-clobazam subgroups. Meta-analysis of subgroups has inherent limitations.
A meta-analysis of 4 RCTs confirmed CBD significantly reduces seizures both with and without clobazam, though the effect was somewhat larger with clobazam
Strong evidence · 10 studies
Post-hoc stratified analysis of existing trials, not prospective; the difference in treatment ratios with/without clobazam could reflect a synergistic effect; cannot fully exclude confounding by cloba
Where questions remain
Preclinical study showing whole cannabis extracts produced faster spasticity relief and more potent anticonvulsant effects than pure THC, with THC-free extracts also showing anticonvulsant activity
Moderate evidence · 31 studies
Both models were preclinical (animal and in vitro). The specific compounds in THC-free extract responsible for anticonvulsant activity were not identified. The mouse spasticity model and brain slice e
Review identified five strategies for making cannabinoid medicines more effective while reducing psychoactive side effects, covering applications from pain to neurodegeneration
Moderate evidence · 31 studies
Many of the proposed therapeutic targets were supported primarily by preclinical data at the time. The strategies are conceptual frameworks that still need to be validated through clinical trials. The
Systematic review of 34 human studies found preliminary CBD benefits for anxiety, insomnia, and epilepsy, with complex THC interactions depending on delivery route
Moderate evidence · 31 studies
Many of the included studies had small sample sizes. The clinical studies covered diverse conditions with different designs, making synthesis difficult. The review captured a relatively early stage of
Expert review found clinical evidence for cannabinoids in MS spasticity, refractory pain, and nausea, with emerging evidence for epilepsy, dystonia, tics, and other neurological conditions
Moderate evidence · 31 studies
The evidence base was limited by small sample sizes in many studies. Safety data were incomplete, especially for long-term use. The wide variety of cannabis preparations and routes of administration m
Research gaps
- Only 4 randomized controlled trials exist out of 210 studies — most evidence is observational or from reviews.
- Long-term prospective studies tracking outcomes over 5+ years are largely absent from the literature.
- Research on diverse populations (different ages, ethnicities, and medical backgrounds) remains limited.
Key studies
Major meta-analysis of 152 RCTs finds cannabinoid effectiveness varies dramatically by specific drug and condition
By analyzing cannabinoid medications separately rather than lumping them together, this study reveals that the question "does cannabis work?" is misleading. The answer depends entirely on which cannabinoid and which condition.
Meta-analysis confirmed CBD reduces seizures by 33% in treatment-resistant epilepsy
This meta-analysis provides the strongest quantitative evidence to date supporting CBD as an add-on treatment for three of the most difficult-to-treat pediatric epilepsy syndromes.
CBD reduced seizures in both Dravet and Lennox-Gastaut syndromes, with enhanced effects when combined with clobazam
This meta-analysis directly addresses the critical question of whether CBD's seizure reduction is partly driven by its interaction with clobazam, showing CBD is effective in both clobazam users and the overall population, but more so in the combination.
CBD does have independent anti-seizure effects, though clobazam interaction boosts them
This addresses the critical question of whether CBD is truly anti-epileptic or merely boosting clobazam levels, concluding that both mechanisms contribute.
Meta-analysis of 4 RCTs confirms CBD reduces seizures with and without clobazam co-treatment
A persistent question has been whether CBD's seizure benefit depends on its interaction with clobazam rather than direct anticonvulsant effects. This meta-analysis demonstrates independent efficacy.
Meta-analysis confirms CBD reduces seizures in Dravet syndrome
Dravet syndrome is among the most severe drug-resistant epilepsies. This meta-analysis provides the highest level of evidence confirming that CBD offers meaningful seizure reduction for these patients.
How the research developed
2000–2009
2 studies published. Predominantly observational and review studies.
2010–2014
11 studies published. Includes 1 strong-evidence studies.
2015–2019
57 studies published. Includes 2 meta-analyses, 1 RCTs, 19 strong-evidence studies.
2020–present
140 studies published. Includes 9 meta-analyses, 3 RCTs, 30 strong-evidence studies.
How this summary was assembled
This consensus synthesizes 210 peer-reviewed studies: 11 meta-analyses (5%), 4 randomized controlled trials (2%), 22 observational studies (10%), 76 reviews (36%), 12 case studies (6%), 85 other study types (40%). Studies span from the earliest available research through 2025. Evidence strength ratings reflect study design, sample size, and replication across multiple research groups.
These counts describe the source summary at publication. They may differ from the current library.