CBD for Lennox-Gastaut Syndrome: The Trial Behind FDA Approval
What Researchers Found About Epilepsy and Cannabis
The Study at a Glance
Published
New England Journal of Medicine, 2018
Researchers
NYU Langone Medical Center (United States)
Study Type
Randomized Controlled TrialParticipants
225 patients · 14 weeks
Key Finding
Children and adults with Lennox-Gastaut syndrome experienced 42% reduction in drop seizures with CBD (20mg/kg/day) compared to 17% with placebo, contributing to FDA approval of Epidiolex.
Key Finding: Children and adults with Lennox-Gastaut syndrome experienced 42% reduction in drop seizures with CBD (20mg/kg/day) compared to 17% with placebo, contributing to FDA approval of Epidiolex.
What Researchers Studied About Epilepsy and Cannabis
Lennox-Gastaut syndrome is a severe form of epilepsy that begins in childhood and causes multiple seizure types, including dangerous "drop seizures" that cause sudden falls. These seizures rarely respond well to conventional medications.
This rigorous clinical trial tested whether pharmaceutical-grade CBD (later branded as Epidiolex) could reduce the frequency of these devastating seizures.
The results of this trial, along with the Dravet syndrome trial, directly led to FDA approval of the first cannabis-derived medication in the United States.
How This Randomized Controlled Trial Was Conducted
This was a randomized, double-blind, placebo-controlled trial:
• 225 patients ages 2-55 with Lennox-Gastaut syndrome • All had at least 2 drop seizures per week despite current medications • Randomly assigned to CBD 20mg/kg/day, 10mg/kg/day, or placebo • Treatment added to existing medications • Seizure frequency tracked for 14 weeks
Epilepsy Treatment Results
The Main Results:
- 142% reduction in drop seizures with CBD 20mg/kg (vs 17% placebo)
- 237% reduction with CBD 10mg/kg dose
- 340% of high-dose patients achieved 50%+ seizure reduction
- 4Significant improvement in overall condition by caregiver assessment
- 5Benefits seen across all seizure types, not just drop seizures
By the Numbers
| Statistic | What It Means |
|---|---|
| 42% | reduction in drop seizures with CBD |
| 17% | reduction with placebo |
| 40% | achieved 50% or greater seizure reduction |
| 225 | patients in this FDA-pivotal trial |
reduction in drop seizures with CBD
reduction with placebo
achieved 50% or greater seizure reduction
patients in this FDA-pivotal trial
What This Means for Epilepsy Patients
This study represents landmark evidence for CBD in severe epilepsy:
Key findings: • CBD significantly reduced dangerous drop seizures • Effects were dose-dependent—higher dose worked better • Benefits extended to other seizure types • This study directly contributed to FDA approval
For patients and families: • Epidiolex is now FDA-approved for Lennox-Gastaut syndrome • It can be prescribed by neurologists and is covered by many insurance plans • It works as an add-on to existing seizure medications
Important notes: • Side effects included drowsiness, decreased appetite, and diarrhea • Liver function should be monitored during treatment
Quick Answers: Epilepsy and Cannabis
Direct answers based on the findings of this study:
Research Summary: Answers are based on published peer-reviewed studies and represent research findings, not medical recommendations. Individual results may vary. Always consult a healthcare provider before making treatment decisions.
Does CBD help Lennox-Gastaut syndrome?
Yes, CBD reduced seizures by 42%. A trial of 225 patients found CBD cut drop seizures by 42%, leading to FDA approval of Epidiolex. 40% of patients had at least half as many seizures (Devinsky et al., NEJM, 2018).
Source: Devinsky et al., New England Journal of Medicine, 2018 (PMID: 29768152)
What is the best treatment for Lennox-Gastaut syndrome?
CBD (Epidiolex) is one FDA-approved option after a trial showed 42% seizure reduction. Talk to a neurologist—LGS usually requires multiple medications, and CBD can be added to existing treatment.
Source: Devinsky et al., New England Journal of Medicine, 2018 (PMID: 29768152)
Does CBD help drop seizures?
Yes, CBD helps drop seizures. In Lennox-Gastaut syndrome trials, CBD reduced dangerous drop seizures by 42% vs 17% with placebo, leading to FDA approval of Epidiolex specifically for LGS.
Source: Devinsky et al., New England Journal of Medicine, 2018 (PMID: 29768152)
This is educational content, not medical advice
The research summarized here is for informational purposes only. Individual results may vary, and what works in studies may not work the same way for everyone. Always consult with a qualified healthcare provider before making changes to your treatment plan or starting medical cannabis therapy.
Important Limitations
This study has some caveats to keep in mind when interpreting the results:
- Study was 14 weeks—long-term efficacy and safety requires longer follow-up
- All patients continued existing medications—can't assess CBD alone
- Higher rates of side effects in CBD groups vs placebo
- Pharmaceutical CBD (Epidiolex) differs from retail CBD products
- Study population had severe, treatment-resistant epilepsy
The Bottom Line on Cannabis for Epilepsy
This pivotal clinical trial proved that CBD significantly reduces dangerous seizures in Lennox-Gastaut syndrome, leading to the FDA approval of Epidiolex. For families dealing with this devastating condition, pharmaceutical CBD offers hope where few effective treatments previously existed.
Do You Qualify for Medical Marijuana?
If you're living with Epilepsy, you may qualify for a medical marijuana card. Our licensed physicians can evaluate you from home via telehealth.
Related Research & Resources
Related Research
Condition Research
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This condition qualifies for medical marijuana in:
Source
Devinsky O, Patel AD, Cross JH, et al. "Effect of Cannabidiol on Drop Seizures in the Lennox-Gastaut Syndrome" New England Journal of Medicine. 2018. DOI: 10.1056/NEJMoa1714631
Important Information
Study Age: This study was published 8 years ago. Newer research may have updated or refined these findings.
Not Medical Advice: This research summary is for educational purposes only. It should not be used to diagnose, treat, cure, or prevent any disease or medical condition. Always consult a qualified healthcare provider before starting or changing any treatment.
Individual Variation: Research findings represent group averages. Your individual response to cannabis may differ based on genetics, other medications, underlying conditions, and many other factors.
Last reviewed: January 24, 2026
Important Notices
Research Summary Disclaimer
This content represents our interpretation of published scientific research for educational purposes. It should not be used to make treatment decisions without consulting a qualified healthcare provider. Individual results may vary from study findings.
FDA Notice
These statements have not been evaluated by the FDA. Cannabis is not intended to diagnose, treat, cure, or prevent any disease. The FDA has not approved cannabis for any medical condition except specific prescription medications.
Copyright & Fair Use
Research summaries are provided under fair use (17 U.S.C. § 107) for educational purposes. We provide brief summaries with attribution, not full reproductions. All studies remain the intellectual property of their respective authors and publishers.
Data Sources
Study information sourced from PubMed®, U.S. National Library of Medicine. Inclusion does not imply endorsement by NLM, NIH, or the federal government.
For complete information, see our Terms of Use and Research Content Policy.
FAQs: Cannabis for Epilepsy
Is CBD FDA-approved for Lennox-Gastaut syndrome?
Yes. Based on this and other clinical trials, Epidiolex (pharmaceutical CBD) was FDA-approved in 2018 for Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex.
How effective is CBD for Lennox-Gastaut seizures?
CBD reduced seizures by 42% vs 17% placebo. In this clinical trial, CBD 20mg/kg/day reduced drop seizures by 42% compared to 17% with placebo. 40% of patients achieved at least a 50% reduction in seizures.
What is Lennox-Gastaut syndrome?
Lennox-Gastaut is a severe childhood epilepsy. It causes multiple seizure types, including "drop seizures" that cause sudden falls. It typically doesn't respond well to conventional treatments, making CBD an important option.