A meta-analysis of 550 patients confirmed CBD reduces seizures in Dravet and Lennox-Gastaut syndromes but increases adverse events
A meta-analysis of four randomized controlled trials involving 550 patients found that adjunctive CBD at 10 and 20 mg/kg/day reduced seizure frequency by about 20 percentage points compared to placebo in Dravet and Lennox-Gastaut syndromes, with higher doses causing more treatment withdrawals and adverse events.
Quick Facts
What This Study Found
Researchers pooled data from four randomized, placebo-controlled trials of oral CBD as add-on therapy in patients with Lennox-Gastaut syndrome (LGS) or Dravet syndrome (DS) whose seizures were not controlled by existing medications.
Both CBD dose levels showed similar efficacy: the pooled difference in seizure frequency reduction was 19.5 percentage points (95% CI 8.1-31.0) for 10 mg/kg/day and 19.9 percentage points (95% CI 11.8-28.1) for 20 mg/kg/day compared to placebo.
The higher dose carried more risk: treatment withdrawal risk was 4.20 times higher for 20 mg/kg/day (95% CI 1.82-9.68) versus placebo but not significantly elevated for 10 mg/kg/day (RR 1.45, 95% CI 0.28-7.41).
Adverse events occurred in 87.9% of CBD patients versus 72.2% on placebo (RR 1.22). The most common side effects were somnolence, decreased appetite, diarrhea, and elevated liver enzymes.
Adverse event-related treatment discontinuation was significantly higher with CBD (8.9% vs 1.8%).
Key Numbers
550 patients across 4 trials. Seizure reduction vs placebo: ~20 percentage points for both doses. Adverse events: 87.9% CBD vs 72.2% placebo. Treatment withdrawal RR for 20 mg: 4.20 (p = .001). Treatment withdrawal RR for 10 mg: 1.45 (not significant). Somnolence, decreased appetite, diarrhea, and elevated aminotransferases were the main side effects.
How They Did This
Systematic review and meta-analysis of four randomized, placebo-controlled, blinded trials. 550 patients with LGS or DS. Risk ratios calculated with 95% confidence intervals via inverse variance method.
Why This Research Matters
This meta-analysis provided key evidence supporting CBD as a treatment for severe childhood epilepsies. The finding that 10 mg/kg/day was similarly effective but safer than 20 mg/kg/day has practical implications for dosing, as it suggests the lower dose may offer a better benefit-risk balance.
The Bigger Picture
This meta-analysis was part of the evidence base that supported FDA approval of Epidiolex (pharmaceutical CBD) for Dravet and Lennox-Gastaut syndromes. It demonstrated that CBD has genuine anti-seizure effects but is not without significant side effects, particularly at higher doses.
What This Study Doesn't Tell Us
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 unregulated CBD products. Short trial durations limit understanding of long-term safety.
Questions This Raises
- ?Is 10 mg/kg/day the optimal dose for balancing efficacy and safety?
- ?Does CBD work in other epilepsy syndromes beyond LGS and DS?
- ?What causes the elevated liver enzymes, and is it clinically significant long-term?
Trust & Context
- Key Stat:
- ~20 percentage point seizure reduction vs placebo at both CBD doses
- Evidence Grade:
- Strong. Meta-analysis of randomized controlled trials with adequate sample size and consistent findings across doses.
- Study Age:
- Published in 2018. CBD (as Epidiolex) has since received FDA approval for these indications, with additional post-marketing safety data available.
- Original Title:
- Efficacy and Safety of Cannabidiol in Epilepsy: A Systematic Review and Meta-Analysis.
- Published In:
- Drugs, 78(17), 1791-1804 (2018)
- Authors:
- Lattanzi, Simona(5), Brigo, Francesco(4), Trinka, Eugen(4), Zaccara, Gaetano, Cagnetti, Claudia, Del Giovane, Cinzia, Silvestrini, Mauro
- Database ID:
- RTHC-01727
Evidence Hierarchy
Combines results from multiple studies to find an overall pattern.
What do these levels mean? →Frequently Asked Questions
Can regular CBD oil from a store treat seizures?
This meta-analysis used pharmaceutical-grade CBD (Epidiolex) at precise, high doses (10-20 mg/kg/day). Over-the-counter CBD products vary widely in actual CBD content, purity, and consistency. These findings apply specifically to pharmaceutical CBD, not unregulated products.
Why did nearly 88% of CBD patients have adverse events?
These were patients with severe epilepsy already on multiple medications. The high adverse event rate partly reflects drug interactions and the overall complexity of their treatment. Somnolence and decreased appetite were the most common CBD-specific effects.
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Cite This Study
https://rethinkthc.com/research/RTHC-01727APA
Lattanzi, Simona; Brigo, Francesco; Trinka, Eugen; Zaccara, Gaetano; Cagnetti, Claudia; Del Giovane, Cinzia; Silvestrini, Mauro. (2018). Efficacy and Safety of Cannabidiol in Epilepsy: A Systematic Review and Meta-Analysis.. Drugs, 78(17), 1791-1804. https://doi.org/10.1007/s40265-018-0992-5
MLA
Lattanzi, Simona, et al. "Efficacy and Safety of Cannabidiol in Epilepsy: A Systematic Review and Meta-Analysis.." Drugs, 2018. https://doi.org/10.1007/s40265-018-0992-5
RethinkTHC
RethinkTHC Research Database. "Efficacy and Safety of Cannabidiol in Epilepsy: A Systematic..." RTHC-01727. Retrieved from https://rethinkthc.com/research/lattanzi-2018-efficacy-and-safety-of
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.