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Medical Marijuana for Epilepsy: What the Research Actually Says

Medical disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making changes to your treatment plan. Medical marijuana laws vary by state — verify the rules in your jurisdiction before proceeding.

Introduction

Of all the conditions for which patients seek medical marijuana, epilepsy stands apart. It is the only condition for which a plant-derived cannabinoid medication has received full approval from the U.S. Food and Drug Administration (FDA). That approval — granted in June 2018 for Epidiolex, a pharmaceutical-grade cannabidiol (CBD) oral solution — marked a turning point not just for epilepsy treatment, but for the broader legitimacy of cannabis-based medicine in the United States.

For the approximately 3.4 million Americans living with epilepsy, and especially for the estimated one-third of those whose seizures cannot be adequately controlled by conventional antiseizure medications (ASMs), this matters enormously. When first-line medications fail, patients and families are left searching for options. Medical cannabis has moved from a fringe anecdote to a peer-reviewed, FDA-validated therapeutic option for certain epilepsy patients — and an area of rapidly expanding research for others.

This article explains what epilepsy is, how the endocannabinoid system interacts with seizure activity, what the clinical evidence shows, which cannabinoids are most relevant, who qualifies for a medical marijuana card on the basis of epilepsy, and what patients should realistically expect.

What Is Epilepsy?

Epilepsy is a chronic neurological disorder characterised by recurrent, unprovoked seizures — abnormal bursts of electrical activity in the brain that temporarily disrupt normal brain function. The condition is not a single disease but rather a spectrum of disorders with over 30 distinct types of seizures and numerous underlying causes, ranging from genetic mutations to brain injury, stroke, infection, and structural abnormalities.

Seizures vary widely in presentation. Some patients experience brief absence seizures — a momentary lapse in awareness that can easily be mistaken for daydreaming. Others experience tonic-clonic (formerly called grand mal) seizures, involving full-body convulsions and loss of consciousness. Between these extremes are dozens of other seizure types including focal aware seizures, atonic (drop) seizures, and myoclonic jerks.

Scale of the condition

  • Approximately 3.4 million people in the United States have active epilepsy (Centers for Disease Control and Prevention, 2024)
  • Around 150,000 new cases of epilepsy are diagnosed in the U.S. each year
  • Epilepsy is the fourth most common neurological disorder after migraine, stroke, and Alzheimer’s disease
  • Roughly 30% of epilepsy patients — approximately 1 million Americans — have treatment-resistant or refractory epilepsy, meaning seizures persist despite trying two or more appropriately chosen and tolerated ASMs (Kaur et al., British Journal of Hospital Medicine, 2025)

For this last group, treatment-resistant epilepsy carries severe consequences: injury from falls during drop seizures, cognitive impairment, depression, social isolation, and a significantly elevated risk of sudden unexpected death in epilepsy (SUDEP). The need for additional therapeutic options is urgent and well-documented.

The Endocannabinoid System and Seizure Control

To understand why cannabis-derived compounds may help control seizures, it helps to understand the endocannabinoid system (ECS) — a regulatory network present throughout the human brain and body that plays a central role in maintaining neurological balance.

The ECS consists of endogenous cannabinoids (endocannabinoids), their receptors (primarily CB1 and CB2 receptors), and the enzymes that synthesise and break them down. CB1 receptors are among the most abundant G-protein coupled receptors in the brain, expressed heavily in regions involved in motor control, memory, emotion, and — critically for epilepsy — excitatory and inhibitory synaptic signalling.

The fundamental problem in epilepsy is an imbalance between excitatory and inhibitory neuronal activity. When excitation overwhelms inhibition, a seizure results. The ECS functions as a natural brake on excessive neuronal activity. When neurons fire too rapidly, they release endocannabinoids that travel backwards across the synapse and bind to CB1 receptors on presynaptic terminals, suppressing the further release of excitatory neurotransmitters — a process called depolarisation-induced suppression of excitation (DSE).

Research has consistently shown that seizures alter the expression and distribution of CB1 receptors. Studies in animal models demonstrate that seizure activity increases the density of CB1 receptors in hippocampal regions (CA1 through CA3), suggesting that the brain attempts to harness the ECS as a natural anti-convulsive mechanism in response to ictal activity (Bhaskaran and Smith, PMC/NIH, 2016).

How CBD acts differently from THC

What makes CBD particularly interesting from a pharmacological standpoint is that its anticonvulsant effects appear to operate through multiple mechanisms, not all of which directly involve CB1 or CB2 receptor binding.

CBD has a low binding affinity for CB1 receptors. Instead, its anticonvulsant properties are attributed to a combination of mechanisms including inhibition of the fatty acid amide hydrolase (FAAH) enzyme — which increases levels of the endocannabinoid anandamide — and direct interactions with serotonin receptors (5-HT1A), transient receptor potential vanilloid 1 (TRPV1) channels, and the GPR55 receptor. Research published in Frontiers in Neuroscience (2025) describes how blocking the 5-HT1A receptor in preclinical models eliminates CBD’s anticonvulsant effect, suggesting serotonergic signalling is a core component of its mechanism.

THC, by contrast, binds directly to CB1 receptors and can exert both pro- and anticonvulsant effects depending on dose, timing, and the individual patient’s neurological profile. At low doses, THC may contribute to seizure suppression by activating CB1 receptors and reducing excitatory neurotransmitter release. At higher doses, however, THC can paradoxically increase seizure risk in some patients, particularly children with developing endocannabinoid systems. This dose-dependent complexity is why pharmaceutical CBD — isolated and standardised — has been the primary focus of clinical research in epilepsy.

The Clinical Evidence: What the Research Shows

The landmark NEJM trials and FDA approval

The modern era of evidence-based cannabis medicine for epilepsy began with the landmark trials conducted by Orrin Devinsky and colleagues, published in the New England Journal of Medicine.

Dravet syndrome (2017): Devinsky et al. published a randomised, double-blind, placebo-controlled trial of CBD in 120 children and young adults with Dravet syndrome — a severe, genetically driven epilepsy that typically begins in the first year of life and is notoriously resistant to conventional medications. Patients receiving CBD experienced a median reduction in monthly convulsive seizures of 38.9%, compared with 13.3% in the placebo group (Devinsky et al., NEJM, 2017). Five percent of patients in the CBD group became seizure-free, compared with none in the placebo group.

Lennox-Gastaut syndrome (2018): A follow-up trial examined 225 patients with Lennox-Gastaut syndrome (LGS) — another severe, treatment-resistant epilepsy characterised by multiple seizure types and intellectual disability. Patients receiving CBD at 20 mg/kg/day experienced a 41.9% reduction in drop seizures compared with a 17.2% reduction in the placebo group (Devinsky et al., NEJM, 2018). Those receiving 10 mg/kg/day experienced a 37.2% reduction. Both doses were statistically superior to placebo.

These results, alongside a third randomised controlled trial in LGS published in The Lancet (Thiele et al., 2018), formed the basis for the FDA’s approval of Epidiolex in June 2018 — the first cannabis plant-derived pharmaceutical to receive FDA approval.

Epidiolex has subsequently received expanded approval for tuberous sclerosis complex (TSC), a genetic condition associated with benign tumours throughout the body and often severely refractory seizures. In 2020, the FDA approved Epidiolex for TSC following a phase III trial that demonstrated significant seizure reduction over placebo.

Real-world evidence from the UK Medical Cannabis Registry

Beyond the controlled trial setting, the UK Medical Cannabis Registry has generated important real-world data. A 2025 analysis published in Brain and Behavior (Cowley et al., Imperial College London Medical Cannabis Research Group) examined outcomes in epilepsy patients prescribed cannabis-based medicinal products (CBMPs). The study found clinically meaningful improvements in quality of life as measured by the QOLIE-31 scale, which assesses seizure worry, overall quality of life, emotional well-being, energy and fatigue, cognitive functioning, medication effects, and social functioning.

A meta-analysis referenced in the same study found that CBD significantly increased the proportion of patients achieving a 50% or greater reduction in seizure frequency compared to placebo — a threshold considered clinically significant in epilepsy trials.

2025 NHS trials and ongoing research

In October 2024, Epilepsy Action announced that two national NHS clinical trials — led by Professor Finbar O’Callaghan and Professor Helen Cross from University College London and Great Ormond Street Hospital — would commence in 2025. The trials will enrol 500 adults and children with treatment-resistant early-onset and genetic generalised epilepsies, randomly assigned to CBD, CBD with a small amount of THC, or placebo over 24 weeks. This represents one of the largest prospective trials of cannabis medicine in epilepsy to date and will significantly advance understanding of whether THC adds therapeutic benefit to CBD for broader epilepsy populations.

A comprehensive review published in Physiological Reviews (American Physiological Society) provides a detailed analysis of both animal and human data on cannabinoids in epilepsy, noting consistent anticonvulsant findings across models while calling for further research in broader epilepsy populations beyond Dravet syndrome and LGS.

A 2025 case series published in Frontiers in Neuroscience reported on 19 patients with drug-resistant epilepsy who achieved seizure freedom following treatment with cannabis-based medicinal products — an outcome that, while requiring cautious interpretation given the observational nature, adds to a growing body of real-world evidence.

What Types of Epilepsy May Benefit?

The strongest evidence currently exists for:

Dravet syndrome — Severe genetic epilepsy beginning in infancy. CBD (Epidiolex) is FDA-approved and has demonstrated significant seizure reduction in multiple RCTs.

Lennox-Gastaut syndrome (LGS) — Characterised by multiple seizure types, intellectual disability, and severe treatment resistance. Epidiolex is FDA-approved for LGS.

Tuberous sclerosis complex (TSC) — A genetic condition causing benign tumours in multiple organs and refractory seizures. Epidiolex received FDA approval for TSC in 2020.

Treatment-resistant focal epilepsy — Evidence is emerging but less definitive. Multiple observational studies and registry analyses suggest meaningful seizure reduction in patients with drug-resistant focal epilepsy treated with CBMPs, though large randomised controlled trials are still needed.

Childhood epilepsy syndromes more broadly — Multiple retrospective studies and expanded-access programmes have reported seizure reduction in children with a range of refractory epilepsies beyond the three FDA-approved indications.

Cannabinoids, Strains, and Products: What to Know

CBD vs THC for epilepsy

For most epilepsy patients — particularly children and those with treatment-resistant forms — CBD-dominant products are the primary focus. The clinical trial evidence that led to FDA approval was based on isolated, pharmaceutical-grade CBD. Most epilepsy-focused physicians recommend starting with a high-CBD, low-THC product.

However, some patients report better outcomes with whole-plant or broad-spectrum products that retain a range of cannabinoids and terpenes. The “entourage effect” hypothesis suggests that minor cannabinoids and terpenes may work synergistically with CBD and THC to enhance therapeutic effect — though this remains an area of active investigation rather than established science.

The 2025 NHS trial’s decision to include a CBD + THC arm reflects growing clinical interest in whether THC contributes anticonvulsant effects that complement CBD.

CBDV (cannabidivarin)

Cannabidivarin (CBDV) is a non-psychoactive cannabinoid structurally similar to CBD that has shown anticonvulsant activity in preclinical models. GW Pharmaceuticals (now Jazz Pharmaceuticals, the maker of Epidiolex) has investigated CBDV under the drug candidate designation GWP42006 for epilepsy, though as of 2026 no CBDV product has received FDA approval.

Recommended approach

Patients pursuing medical cannabis for epilepsy outside of the Epidiolex pathway should work directly with a neurologist or epileptologist who has experience with cannabis-based medicine. Self-medicating for epilepsy — particularly in children — carries real risks. Abrupt changes to a seizure management regimen can trigger breakthrough seizures or status epilepticus. Any cannabis-based treatment should be introduced gradually, with full monitoring, and in coordination with the prescribing neurologist.

Dosing Considerations

Dosing for seizure disorders is highly individualised and should always be managed by a physician. That said, the clinical trial data gives useful reference points:

  • The Dravet and LGS trials of Epidiolex used doses of 10 mg/kg/day and 20 mg/kg/day in two divided doses
  • The FDA-approved prescribing information for Epidiolex begins at a starting dose of 2.5 mg/kg twice daily (5 mg/kg/day), with gradual titration
  • For patients accessing cannabis-based products outside the Epidiolex pathway, the principle of “start low, go slow” is standard — typically beginning with a very low CBD dose and titrating upward over weeks to months based on response and tolerability

Dosing for broader epilepsy populations is not standardised outside the approved indications, which is one reason that working with a knowledgeable clinician is essential.

Potential Side Effects and Drug Interactions

CBD is generally well tolerated, but it is not side-effect free. The most commonly reported adverse effects in the clinical trials of Epidiolex included:

  • Somnolence (drowsiness) — the most common adverse effect, reported in approximately 25% of patients in the Dravet trial
  • Decreased appetite
  • Diarrhoea
  • Elevated liver enzymes (transaminases) — particularly when used concurrently with valproate (valproic acid), a common antiseizure medication. The FDA prescribing information requires monitoring of liver function before and during treatment
  • Fatigue and irritability

Drug interactions

CBD is metabolised by cytochrome P450 enzymes (primarily CYP3A4 and CYP2C19) and inhibits several others. This creates the potential for clinically significant interactions with antiseizure medications that share these pathways. Known interactions include:

  • Valproate — CBD increases valproate exposure and risk of liver toxicity when combined
  • Clobazam — CBD significantly increases plasma levels of the active metabolite of clobazam (N-desmethylclobazam), which may enhance both efficacy and sedation
  • Stiripentol, rufinamide, topiramate, zonisamide — interactions documented; dose adjustments may be needed

Any patient using conventional antiseizure medications who wishes to add cannabis-based products must discuss these interactions in detail with their neurologist and pharmacist. This is not optional — unmonitored drug interactions in epilepsy can have serious consequences.

Does Epilepsy Qualify for a Medical Marijuana Card?

Epilepsy is among the most widely recognised qualifying conditions for medical marijuana programs across the United States. As of 2026, epilepsy or seizure disorders appear on the qualifying condition list in the large majority of states with active MMJ programs.

Because state programs vary, it is important to check the specific qualifying condition list for your state. Generally speaking:

  • States that include “epilepsy” as a named condition will typically require documentation of a formal diagnosis from a neurologist or physician, along with evidence that the condition has been inadequately controlled (i.e., treatment-resistant)
  • Some states use broader language such as “seizure disorders” or “intractable epilepsy,” which may have slightly different documentation requirements
  • Patients who already receive Epidiolex by prescription have a clearly documented qualifying diagnosis and generally face fewer barriers

How to access a medical marijuana card for epilepsy

Step 1: Confirm epilepsy is listed as a qualifying condition in your state. Use our state-by-state MMJ card guide to verify.

Step 2: Gather your medical records. You will typically need documentation of your epilepsy diagnosis, current medications, and evidence that seizures have not been adequately controlled. Records from a neurologist carry particular weight.

Step 3: Consult a licensed MMJ physician. Telehealth MMJ consultations (available through services like NuggMD, Leafwell, and Veriheal) allow patients to meet with a state-licensed physician online. The consultation typically takes 15–20 minutes.

Step 4: Receive your recommendation. If approved, your physician will issue a written recommendation. In most states, this can be taken directly to a licensed dispensary or used to register with the state’s patient registry.

Step 5: Register with your state (if required). Some states require patients to submit their physician recommendation to a state health department registry before accessing medical marijuana dispensaries.

What to Tell Your Doctor

Approaching a neurologist or MMJ physician about cannabis for epilepsy is most productive when you come prepared. Consider discussing:

  • Your complete seizure history: types, frequency, duration, triggers
  • All current and previously tried antiseizure medications and their outcomes
  • Any previous experience with cannabis or CBD products
  • Specific goals: are you seeking adjunctive treatment to reduce seizure frequency, or exploring cannabis as a replacement for a medication with intolerable side effects?
  • Concerns about drug interactions with your current medications

Patients with epilepsy who have a relationship with a neurologist should ideally involve that neurologist in any decision to add cannabis-based treatment, even if the MMJ card is obtained through a separate telehealth provider. Epilepsy management should be coordinated — not fragmented.

Frequently Asked Questions

Can cannabis cure epilepsy? No. There is no evidence that cannabis or cannabinoids cure epilepsy or permanently alter its underlying cause. The evidence supports cannabis — particularly CBD — as a treatment that can meaningfully reduce seizure frequency in some patients, particularly those with treatment-resistant forms of epilepsy.

Is Epidiolex the same as medical marijuana? Not exactly. Epidiolex is a pharmaceutical-grade, FDA-approved oral solution of isolated CBD derived from the cannabis plant. It is a prescription medication with defined dosing, quality controls, and a formal prescribing label. It is different from dispensary-purchased cannabis products, which vary widely in cannabinoid content and are not FDA-approved medicines. However, CBD is the same molecule in both.

Can children with epilepsy use medical marijuana? The FDA has approved Epidiolex for patients aged 1 year and older for Dravet syndrome, LGS, and TSC. For children, any cannabis-based treatment should be managed by a paediatric neurologist with experience in this area. Most states’ medical marijuana programs include provisions for paediatric patients with qualifying conditions.

Will cannabis interact with my current seizure medications? Potentially yes, and this is one of the most important considerations in epilepsy specifically. CBD in particular has well-documented interactions with several antiseizure medications, most notably valproate and clobazam. Always consult your neurologist and pharmacist before adding any cannabis-based product.

What if my state does not list epilepsy as a qualifying condition? If you have treatment-resistant epilepsy and your state does not list epilepsy as a qualifying condition, your neurologist may be able to prescribe Epidiolex directly through the standard pharmaceutical prescription pathway — no MMJ card needed. Epidiolex is a Schedule V controlled substance and can be prescribed by any licensed physician with an active DEA registration.

Key Takeaways

  • Epilepsy has more clinical evidence supporting cannabis-based treatment than almost any other condition, culminating in the FDA approval of Epidiolex for Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex
  • The evidence base centres on CBD, not THC — CBD appears to work through multiple mechanisms to reduce neuronal excitability and seizure frequency
  • Approximately 30% of epilepsy patients have treatment-resistant disease; this group has the most to gain and the most clinical data supporting cannabis-based intervention
  • Drug interactions are a serious consideration — CBD interacts with valproate, clobazam, and other common antiseizure medications and must be managed by a qualified clinician
  • Epilepsy qualifies for a medical marijuana card in the majority of US states with active MMJ programs
  • Any cannabis-based treatment for epilepsy should be initiated in coordination with a neurologist, not as a self-managed substitution for conventional care

Sources and Further Reading

  1. Devinsky, O., Cross, J.H., Laux, L., et al. (2017). Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome. New England Journal of Medicine, 376, 2011–2020. https://doi.org/10.1056/NEJMoa1611618
  2. Devinsky, O., Patel, A.D., Cross, J.H., et al. (2018). Effect of Cannabidiol on Drop Seizures in the Lennox–Gastaut Syndrome. New England Journal of Medicine, 378, 1888–1897. https://doi.org/10.1056/NEJMoa1714631
  3. Thiele, E.A., Marsh, E.D., French, J.A., et al. (2018). Cannabidiol in patients with seizures associated with Lennox-Gastaut syndrome (GWPCARE4): a randomised, double-blind, placebo-controlled phase 3 trial. The Lancet, 391(10125), 1085–1096. https://doi.org/10.1016/S0140-6736(18)30136-3
  4. Kaur, V., Deacon, H., Barnes, M.P., & Nutt, D.J. (2025). Medical Cannabis and Epilepsy: The Evidence. British Journal of Hospital Medicine, 86(11), 1–20. https://doi.org/10.12968/hmed.2024.0903
  5. Cowley, I., Erridge, S., Aggarwal, A., et al. (2025). UK Medical Cannabis Registry: A Clinical Outcomes Analysis for Epilepsy. Brain and Behavior, 15(4), e70490. https://doi.org/10.1002/brb3.70490
  6. Kaur, V. et al. (2025, April). 19 patients report seizure freedom with medical cannabis oil treatment for drug-resistant epilepsy: a case series. Frontiers in Neuroscience. https://doi.org/10.3389/fnins.2025.1570531
  7. Miller, I., Scheffer, I.E., Gunning, B., et al. (2020). Dose-Ranging Effect of Adjunctive Oral Cannabidiol vs Placebo on Convulsive Seizure Frequency in Dravet Syndrome. JAMA Neurology, 77(5), 613–621. https://doi.org/10.1001/jamaneurol.2020.0073
  8. Bhaskaran, M.D. & Smith, B.N. (2016). Medical Marijuana for Epilepsy? PMC/NIH, PMC4911937. https://pmc.ncbi.nlm.nih.gov/articles/PMC4911937/
  9. Lattanzi, S., et al. (2018). Epilepsy and Cannabis: A Literature Review. PMC/NIH, PMC6235654. https://pmc.ncbi.nlm.nih.gov/articles/PMC6235654/
  10. FDA Prescribing Information — Epidiolex (cannabidiol) oral solution (2025 update). U.S. Food and Drug Administration. https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/210365s023lbl.pdf
  11. Epilepsy Action (October 2024). Cannabis medicine trials for refractory epilepsy to start in 2025. https://www.epilepsy.org.uk/news/cannabis-medicine-trials-for-refractory-epilepsy-to-start-in-2025
  12. Centers for Disease Control and Prevention (2024). Epilepsy Data and Statistics. https://www.cdc.gov/epilepsy/data/index.html