Long-term CBD for Lennox-Gastaut: 48-60% Seizure Reduction Sustained
What Researchers Found About Epilepsy and Cannabis
The Study at a Glance
Published
Epilepsia, 2019
Researchers
Multiple institutions (International)
Study Type
Observational StudyParticipants
366 patients · Median 38 weeks
Key Finding
Long-term add-on CBD treatment had an acceptable safety profile in patients with LGS and led to sustained reductions in seizures.
Key Finding: Long-term add-on CBD treatment had an acceptable safety profile in patients with LGS and led to sustained reductions in seizures.
What Researchers Studied About Epilepsy and Cannabis
Patients with Lennox-Gastaut syndrome (LGS) who completed one of two randomized controlled trials (GWPCARE3 or GWPCARE4) were invited to enroll in an open-label extension study.
This study evaluated long-term safety and efficacy of pharmaceutical CBD (Epidiolex).
Of 368 patients who completed the original RCTs, 366 (99.5%) enrolled in this extension.
How This Observational Study Was Conducted
Patients received pharmaceutical CBD oral solution (Epidiolex; 100 mg/mL), titrated from 2.5 to 20 mg/kg/day over a 2-week titration period, added to their existing medications.
Doses could be reduced if not tolerated or increased up to 30 mg/kg/day if beneficial.
Median treatment duration was 38 weeks at a mean modal dose of 23 mg/kg/day. This interim analysis was based on a November 2016 data cut.
Epilepsy Treatment Results
The Main Results:
- 1366 patients enrolled (99.5% of those completing original RCTs)
- 2Median treatment duration: 38 weeks at mean dose of 23 mg/kg/day
- 3Drop seizures: 48-60% median reduction from baseline through week 48
- 4Total seizures: 48-57% median reduction from baseline through week 48
- 588% of patients/caregivers reported improvement on Global Impression of Change
- 6Adverse events in 92.1% of patients (mild 32.5%, moderate 43.4%)
- 7Common AEs: diarrhea (26.8%), somnolence (23.5%), convulsion (21.3%)
- 89.6% (35 patients) discontinued due to adverse events
- 9Liver transaminase elevations in 10.1% (37 patients), 29 on valproic acid
By the Numbers
| Statistic | What It Means |
|---|---|
| 366 patients | LGS patients enrolled in long-term extension (99.5% of eligible) |
| 48-60% | Median reduction in drop seizures sustained through 48 weeks |
| 88% | Patients/caregivers reporting improvement on Global Impression scale |
| 10.1% | Patients with liver transaminase elevations (mostly on valproic acid) |
LGS patients enrolled in long-term extension (99.5% of eligible)
Median reduction in drop seizures sustained through 48 weeks
Patients/caregivers reporting improvement on Global Impression scale
Patients with liver transaminase elevations (mostly on valproic acid)
What This Means for Epilepsy Patients
This study provides important long-term data on CBD for Lennox-Gastaut syndrome, one of the most severe forms of childhood epilepsy.
Nearly all patients (99.5%) who completed the original trials chose to continue CBD, suggesting they found it beneficial. Over a median of 38 weeks, CBD maintained substantial seizure reductions: drop seizures decreased by 48-60% and total seizures by 48-57%.
Perhaps most meaningfully, 88% of patients or caregivers reported improvement in overall condition.
While adverse events were common (92.1%), most were mild to moderate. The main concern is liver enzyme elevations in 10.1% of patients, particularly those also taking valproic acid, though most cases resolved with dose adjustments.
For families dealing with LGS, this confirms CBD can provide sustained benefit over the long term.
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.
How long can you take CBD for Lennox-Gastaut syndrome?
Yes, CBD can be taken safely long-term. 366 LGS patients took CBD for a median of 38 weeks with sustained seizure reduction (48-60% for drop seizures) and acceptable safety.
Source: Thiele et al., Epilepsia, 2019 (PMID: 30740695)
Does CBD keep working for LGS seizures over time?
Yes. In a 366-patient extension study, CBD maintained its effect through 48 weeks: drop seizures reduced 48-60%, total seizures reduced 48-57%. 88% of patients/caregivers reported continued improvement.
Source: Thiele et al., Epilepsia, 2019 (PMID: 30740695)
What monitoring is needed for long-term CBD in LGS?
Liver function monitoring is essential, especially with valproic acid (10.1% had elevated enzymes, mostly on valproate). Common long-term side effects include diarrhea (26.8%), sleepiness (23.5%), and seizures (21.3%). 9.6% discontinued due to adverse events.
Source: Thiele et al., Epilepsia, 2019 (PMID: 30740695)
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:
- Open-label design (no placebo comparison in extension)
- Adverse events in 92.1% of patients
- 9.6% discontinued due to adverse events
- Liver monitoring required, especially with valproic acid
- Cannot separate CBD effect from natural disease fluctuation
The Bottom Line on Cannabis for Epilepsy
This open-label extension of 366 LGS patients shows CBD benefits are sustained long-term. Over 38 weeks median treatment, drop seizures decreased 48-60% and total seizures 48-57%. 88% reported improvement. Adverse events were common (92.1%) but mostly mild/moderate. Liver monitoring is essential, especially with valproic acid (10.1% had elevations). This confirms CBD as a viable long-term option for LGS.
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
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Source
Thiele E, Marsh E, Mazurkiewicz-Beldzinska M, et al. "Cannabidiol in patients with Lennox-Gastaut syndrome: Interim analysis of an open-label extension study" Epilepsia. 2019. DOI: 10.1111/epi.14670
Important Information
Study Age: This study was published 7 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 25, 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
Does CBD work long-term for Lennox-Gastaut syndrome?
Yes. In this extension study of 366 patients, CBD maintained its seizure-reducing effect over a median of 38 weeks. Drop seizures were reduced 48-60% and total seizures 48-57%. 88% of patients/caregivers reported improvement.
What are the long-term side effects of CBD for LGS?
Adverse events occurred in 92.1% of patients but were mostly mild (32.5%) or moderate (43.4%). Common side effects were diarrhea (26.8%), sleepiness (23.5%), and seizures (21.3%). 9.6% discontinued due to adverse events.
Is CBD safe with valproic acid for epilepsy?
Caution is needed. In this study, 10.1% of patients had liver enzyme elevations, and 29 of 37 affected patients were taking valproic acid. Most cases resolved with dose adjustments. Regular liver monitoring is recommended.