Cannabis and Epilepsy: What Prescription CBD Trials Show

Can cannabis help epilepsy? For a few rare forms, yes: in randomized trials, prescription CBD reduced seizures in Dravet and Lennox-Gastaut syndromes, but NIH says there is not enough research on more common forms. The trials used purified prescription CBD, now sold as Epidiolex, not store-bought products.

Historians often trace some of the oldest written accounts of epilepsy to ancient Babylonian medical texts. Back then, the brain’s role was not understood, and seizures were widely blamed on the supernatural. The Hippocratic treatise On the Sacred Disease is often cited as an early argument that epilepsy starts in the brain.
Medicinal use of cannabis goes back at least 3,000 years, and Western medicine has tried it for convulsions since 1839, according to the National Cancer Institute.

What is Epilepsy?

Epilepsy is known as a seizure disorder, a neurological condition which affects the central nervous system. It causes recurring seizures, and doctors use brain scans and other tests to diagnose it.
The seizures happen when clusters of nerve cells, or neurons, in the brain send out the wrong signals, and people may feel strange sensations or emotions. Epilepsy can follow illness, brain injury or abnormal brain development, but in many cases the cause is unknown.

About 2.9 million U.S. adults had active epilepsy in 2021 and 2022, and about 456,000 children have it, according to CDC. Almost a third of people with epilepsy have seizures that medicines do not control.
The severity and type of seizures associated with epilepsy can vary. In the more serious seizures, people may have violent muscle spasms or lose consciousness, MedlinePlus explains. There are also less severe forms of seizures associated with the disease.

Cannabis for the Treatment of Epilepsy

Randomized placebo-controlled trials in Dravet syndrome and Lennox-Gastaut syndrome now show that prescription cannabidiol (CBD) reduces seizures in these rare epilepsies. Epidiolex, a purified CBD medicine, is FDA-approved for seizures from Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis complex in patients 1 year and older. Dravet and Lennox-Gastaut syndromes are rare forms of epilepsy that often result in uncontrolled seizures.

An earlier open-label study, published in 2016, gave purified CBD to people with treatment-resistant epilepsy at 11 U.S. epilepsy centers. The study enrolled 214 patients, who took oral CBD alongside their usual seizure medicines; 162 with at least 12 weeks of follow-up were in the safety analysis and 137 in the efficacy analysis.
The median drop in monthly motor seizures was 36.5%, but with no placebo group the study could not prove CBD caused it.

The journal Epilepsy and Behavior published a 2017 report of retrospective data on how patients responded to artisanal cannabis for epilepsy. Of 272 combined patients from Washington and California, 14% found that artisanal cannabis extracts had no effect. 15% experienced a 1-25% reduction in seizures. 18% experienced a 26-50% reduction in seizures. 17% experienced a 51-75% reduction in seizures. 28% experienced a 76-99% reduction in seizures, and 10% experienced a complete clinical response.
That study was a retrospective review with no comparison group, so it cannot show that artisanal extracts work where approved medicines failed.

Side Effects of Cannabis in Epilepsy Patients

In trials, the most common side effects of prescription CBD were sleepiness, decreased appetite, diarrhea and fatigue, and the FDA warns CBD can harm the liver and interact with other drugs. In the 2016 open-label study, 3% of patients stopped because of side effects.

Cannabis Strains Named in Epilepsy Stories

No strain has been proven to treat seizures. The products below are known by name among families, but none is FDA-approved, and their content can differ from the label.

• Charlotte’s Web: This low-THC plant is reported to have been bred by Colorado growers for a young patient named Charlotte who had Dravet syndrome. As a hemp product, it must contain no more than 0.3% delta-9 THC by dry weight under federal law today. From November 12, 2026, the federal hemp definition leaves out products with cannabinoids the cannabis plant cannot produce naturally, and a 2026 law delays its 0.4 mg total THC per container limit until December 11, 2026.
• Haleigh’s Hope: Another strain that was developed with its namesake in mind. Haleigh suffered from both cerebral palsy and epilepsy. This hybrid is reported to have a CBD to THC ratio of about 24:1. That is one family’s account, not a clinical result.
• Valentine X: Reportedly named for St. Valentine, whom Christian tradition links with epilepsy. Growers describe it as a hybrid with roughly equal THC and CBD, though products vary. There are no published trials of this strain for seizures.

The Takeaway

As with many medical uses of cannabis, its effectiveness and safety in epilepsy need more study. Trials support prescription CBD for a few rare epilepsies, but NIH says there is not enough research to know whether cannabinoids help more common forms of epilepsy. People with hard-to-control seizures should ask their neurologist about prescription CBD and other options before trying store-bought cannabis products. Always speak with a physician before adding cannabis to your current medications. In Florida, epilepsy is one of the qualifying conditions listed in s. 381.986, and our Florida medical marijuana card page explains how certification works.

Last updated October 15, 2026 by the Dr. Green Relief Editorial Team.

Sources

• Devinsky O et al. Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome. N Engl J Med. 2017 (PubMed)
• Thiele EA et al. Cannabidiol in patients with seizures associated with Lennox-Gastaut syndrome (GWPCARE4). Lancet. 2018 (PubMed)
• Devinsky O et al. Cannabidiol in patients with treatment-resistant epilepsy: an open-label interventional trial. Lancet Neurol. 2016 (PubMed)
• Sulak D et al. The current status of artisanal cannabis for the treatment of epilepsy in the United States. Epilepsy Behav. 2017 (PubMed)
• MedlinePlus, Epilepsy
• Centers for Disease Control and Prevention, Epilepsy Facts and Stats
• National Cancer Institute, Cannabis and Cannabinoids (PDQ), history section
• National Center for Complementary and Integrative Health, Cannabis (Marijuana) and Cannabinoids: What You Need To Know
• U.S. Food and Drug Administration, What You Need to Know About Products Containing Cannabis or CBD