Does CBD reduce seizures?

Q: Does CBD reduce seizures?

Yes, purified prescription CBD has reduced specific seizure types in randomized trials involving Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex when added to other antiseizure medicines.

Q: Does CBD work for every type of epilepsy?

No. Evidence differs by syndrome and seizure type. Research beyond the best-established syndromes is often promising but is mostly open-label or observational.

Q: Is prescription CBD the same as store-bought CBD?

No. The strongest trials used standardized purified prescription oral CBD at weight-based doses. Consumer products can differ in formulation, dose accuracy, purity, and other ingredients.

Q: What side effects were reported?

Studies reported effects including sleepiness or sedation, diarrhea, appetite changes, liver-enzyme elevations, adverse-event withdrawals, and medicine interactions. The exact pattern changed by dose and other medicines.

The short answer

What is the bottom line?

Yes, for specific seizures and specific prescription use. Purified prescription CBD has reduced convulsive seizures in Dravet syndrome, drop seizures in Lennox-Gastaut syndrome, and seizures associated with tuberous sclerosis complex when it was added to other antiseizure medicines. ¹ ² ³ ⁴

The evidence is not a blanket result for every epilepsy. Studies in focal epilepsy, CDKL5 deficiency disorder, epileptic spasms, monogenic epilepsies, and broader developmental epileptic encephalopathies often report improvement, but most are open-label, retrospective, or otherwise lack a placebo group. ⁸ ⁹ ¹⁰

The product also matters. Most controlled trials used a standardized purified oral CBD medicine at weight-based doses. CBD-enriched cannabis oil and over-the-counter products are different formulations. Dose, clobazam or valproate use, sedation, diarrhea, liver-enzyme elevations, and treatment discontinuation can change the clinical picture. ^source ¹¹ ¹²

What this means: CBD is not merely a promising theory for seizures; it has controlled human evidence for several severe epilepsy syndromes. The careful answer is positive for those uses, while broader seizure types and nonprescription products still have less certain evidence. ¹ ² ³ ⁴ ⁸ ⁹ ¹⁰

How to read this answer: Research has examined Does CBD reduce seizures?. This page brings together 24 human-study sources, 20 research reviews, and 1 lab, animal, or mechanism source. It includes 51 specific study findings from 26 sources. The source set includes human research as well as earlier-stage studies. The studies do not all test the same product, dose, group of people, or outcome, so they cannot be reduced to one answer for every person or product. ¹

Key takeaways

What to know first

1
The strongest evidence is for purified prescription CBD used with other antiseizure medicines in Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex. ¹
2
Evidence in other epilepsies is often encouraging, but most of it comes from studies without a placebo group. ²
3
Prescription CBD is not interchangeable with store-bought CBD, and side effects, liver monitoring, dose, and medicine interactions matter. ³

Choose your question

What do you want to know about CBD and seizures?

Seizure studies do not all measure the same event or test the same product. Start with the question closest to what you want to understand.

01Seizure question

Which epilepsies have the strongest evidence?
Start with randomized evidence for Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex.
See the evidence
02Seizure question

What about other seizure disorders?
See what open-label and real-world studies found in focal, genetic, developmental, and rarer epilepsies.
See the evidence
03Seizure question

How much improvement was reported?
Compare seizure-frequency changes, responder rates, seizure days, caregiver ratings, and seizure freedom without treating them as the same outcome.
See the evidence
04Seizure question

What changes the answer?
Check formulation, dose, other antiseizure medicines, adverse events, liver findings, and whether a study had a placebo group.
See the evidence

Research areas

What researchers studied about CBD and seizures

The evidence is strongest when the epilepsy syndrome, seizure type, formulation, and comparator are named clearly.

Controlled evidence

Dravet syndrome

Trials measured convulsive seizures, nonconvulsive seizures, caregiver-rated change, dose exposure, and adverse events after purified CBD was added to existing medicines. ¹ ^source

Controlled evidence

Lennox-Gastaut syndrome

Trials focused on drop seizures and compared different weight-based CBD doses with placebo. Later analyses asked how much seizure reduction aligned with caregiver-noticed improvement. ² ³ ⁶

Controlled evidence

Tuberous sclerosis complex

A randomized trial measured TSC-associated seizures at two CBD doses and reported diarrhea, somnolence, liver-enzyme elevations, and discontinuation. ⁴

Promising, mostly uncontrolled

Other and rarer epilepsies

Real-world and open-label studies examined focal epilepsy, CDKL5 deficiency disorder, epileptic spasms, monogenic epilepsies, developmental epileptic encephalopathies, and chromosome 15 syndromes. ⁹ ^source ^source

Study-by-study results

What did the CBD seizure studies report?

Each result-bearing study appears once. Its measured outcomes, formulation, dose, duration, comparator, limitations, and PubMed source stay together so unlike results are not blended into one number.

01

Where is the strongest evidence?

Randomized trials and trial-based analyses provide the clearest evidence. They focus on purified prescription CBD added to existing antiseizure medicines.

Study details

Dravet syndrome randomized trial

PubMed 28538134

Study type: randomized double-blind placebo-controlled trial
Population: 120 children and young adults with Dravet syndrome and drug-resistant seizures
Formulation: cannabidiol oral solution
Dose: 20 mg/kg/day
Duration: 14 weeks
Comparator: placebo

Measured outcomes

Improvement reported

monthly convulsive-seizure frequency

Median frequency decreased from 12.4 to 5.9 with CBD and from 14.9 to 14.1 with placebo; adjusted median difference -22.8 percentage points (95% CI -41.1 to -5.4; P=0.01). ¹

Improvement reported

caregiver-rated overall condition improvement

Improvement in 62% of the CBD group and 34% of the placebo group (P=0.02). ¹

No difference detected

nonconvulsive-seizure frequency

The abstract reports no significant reduction in nonconvulsive seizures. ¹

Keep in mind: The trial enrolled patients with Dravet syndrome and may not generalize to other epilepsies. CBD was added to existing antiseizure treatment. The treatment period was 14 weeks.

Study details

Lennox-Gastaut GWPCARE4 trial

PubMed 29395273

Study type: randomized double-blind placebo-controlled phase 3 trial
Population: 171 patients aged 2-55 with treatment-resistant Lennox-Gastaut syndrome
Formulation: oral cannabidiol
Dose: 20 mg/kg/day
Duration: 14 weeks
Comparator: matched placebo

Measured outcomes

Improvement reported

monthly drop-seizure frequency

Median reduction 43.9% with CBD and 21.8% with placebo; estimated median difference -17.21 (95% CI -30.32 to -4.09; P=0.0135). ²

Safety or tolerability finding

adverse-event frequency

Adverse events occurred in 86% of the CBD group and 69% of the placebo group. ²

Safety or tolerability finding

withdrawal due to adverse events

Withdrawal due to adverse events occurred in 14% of the CBD group and 1% of the placebo group. ²

Keep in mind: The trial enrolled patients with Lennox-Gastaut syndrome and may not generalize to other epilepsies. CBD was used as add-on therapy. The treatment period was 14 weeks.

Study details

Lennox-Gastaut two-dose trial

PubMed 29768152

Study type: randomized double-blind placebo-controlled trial
Population: 225 patients aged 2-55 with Lennox-Gastaut syndrome
Formulation: cannabidiol oral solution
Dose: 20 mg/kg/day; 10 mg/kg/day
Duration: 14 weeks
Comparator: matching placebo

Measured outcomes

Improvement reported

drop-seizure frequency

Median reduction 41.9% with 20 mg/kg/day and 17.2% with placebo (P=0.005). ³

Improvement reported

drop-seizure frequency

Median reduction 37.2% with 10 mg/kg/day and 17.2% with placebo (P=0.002). ³

Keep in mind: The trial enrolled patients with Lennox-Gastaut syndrome and may not generalize to other epilepsies. CBD was added to conventional antiseizure medication. The treatment period was 14 weeks.

Study details

Tuberous sclerosis complex randomized trial

PubMed 33346789

Study type: randomized double-blind placebo-controlled clinical trial
Population: 224 patients aged 1-65 with tuberous sclerosis complex and medication-resistant epilepsy
Formulation: oral cannabidiol
Dose: 25 mg/kg/day; 50 mg/kg/day; 25 or 50 mg/kg/day
Duration: 16 weeks
Comparator: matched placebo

Measured outcomes

Improvement reported

TSC-associated seizure frequency

Reduction from baseline 48.6% with 25 mg/kg/day and 26.5% with placebo; reduction from placebo 30.1% (95% CI 13.9%-43.3%; P<0.001). ⁴

Improvement reported

TSC-associated seizure frequency

Reduction from baseline 47.5% with 50 mg/kg/day and 26.5% with placebo; reduction from placebo 28.5% (95% CI 11.9%-42.0%; nominal P=0.002). ⁴

Safety or tolerability finding

diarrhea frequency

Diarrhea occurred in 31% with 25 mg/kg/day and 25% with placebo. ⁴

Safety or tolerability finding

diarrhea frequency

Diarrhea occurred in 56% with 50 mg/kg/day and 25% with placebo. ⁴

Safety or tolerability finding

somnolence frequency

Somnolence occurred in 13% with 25 mg/kg/day and 9% with placebo. ⁴

Safety or tolerability finding

somnolence frequency

Somnolence occurred in 26% with 50 mg/kg/day and 9% with placebo. ⁴

Safety or tolerability finding

treatment discontinuation due to adverse events

Eight patients in the 25 mg/kg/day group, 10 in the 50 mg/kg/day group, and two in the placebo group discontinued because of adverse events. ⁴

Safety or tolerability finding

elevated liver transaminase frequency

Elevated liver transaminases occurred in 18.9% of CBD-treated patients and no placebo-treated patients. ⁴

Keep in mind: The trial enrolled patients with tuberous sclerosis complex-associated epilepsy. CBD was used with at least one existing antiseizure medication. The treatment period was 16 weeks.

Study details

Dravet dose and interaction trial

PubMed 29540584

Study type: randomized double-blind placebo-controlled dose-ranging safety trial
Population: 34 children aged 4 to 10 years with Dravet syndrome
Formulation: pharmaceutical formulation of purified CBD
Dose: 5, 10, or 20 mg/kg/day in two daily doses
Duration: 3-week treatment period including titration
Comparator: placebo

Measured outcomes

Drug exposure changed

CBD and metabolite exposure as CBD dose increases

CBD and metabolite AUC0-t increased proportionally across the studied doses. ^source

Drug exposure changed

N-desmethylclobazam exposure

N-desmethylclobazam increased, except among participants taking stiripentol; the abstract provides no effect estimate. ^source

Safety or tolerability finding

adverse-event frequency

The abstract classifies the trial as Class I evidence that CBD produced more adverse events than placebo; group counts are not provided. ^source

Keep in mind: The trial randomized 34 children and lasted three treatment weeks including titration. CBD was used with concomitant antiseizure medications. The study was designed primarily for safety and preliminary pharmacokinetics, not seizure efficacy.

Study details

Caregiver-meaningfulness analysis

PubMed 40775196

Study type: exploratory post hoc analysis of two phase 3 randomized trials
Population: 215 CBD-treated patients aged 2 to 55 years with Lennox-Gastaut syndrome
Formulation: Epidiolex or Epidyolex 100 mg/mL CBD oral solution
Dose: trial doses varied across the two parent studies
Duration: 14 weeks
Comparator: threshold analysis within CBD-treated trial participants

Measured outcomes

Improvement reported

drop-seizure reduction associated with slight-or-better caregiver improvement

A 30.6% drop-seizure reduction best aligned with caregiver ratings of slight-or-better improvement; 57.7% met that threshold. ⁶

Keep in mind: This was an exploratory post hoc threshold analysis, not a new randomized efficacy comparison. The analysis included only CBD-treated participants with recorded caregiver ratings. The result applies to drop seizures in Lennox-Gastaut syndrome.

Study details

Randomized-trial meta-analysis

PubMed 40267856

Study type: systematic review and meta-analysis of randomized controlled trials
Population: 575 participants across 4 CBD randomized trials for the 20 mg/kg/day estimate; 280 participants across 2 CBD randomized trials for the 10 mg/kg/day estimate; 583 participants across 4 CBD randomized trials for the serious-adverse-event estimate
Formulation: cannabidiol 20 mg/kg/day; cannabidiol 10 mg/kg/day
Dose: 20 mg/kg/day; 10 mg/kg/day
Duration: varied across included trials
Comparator: placebo or trial control

Measured outcomes

Improvement reported

at-least-50-percent monthly seizure response at 20 mg/kg/day in randomized trials

CBD 20 mg/kg/day increased the chance of at least 50% monthly seizure reduction (RR 1.92; 95% CI 1.49 to 2.46; moderate certainty). ⁵

Improvement reported

at-least-50-percent monthly seizure response at 10 mg/kg/day in randomized trials

CBD 10 mg/kg/day increased the chance of at least 50% monthly seizure reduction (RR 1.94; 95% CI 1.32 to 2.86; moderate certainty). ⁵

Safety or tolerability finding

serious adverse-event risk at 20 mg/kg/day in randomized trials

Serious adverse events were more frequent with 20 mg/kg/day CBD (RR 2.30; 95% CI 1.36 to 3.89; moderate certainty). ⁵

Keep in mind: The estimate pools four randomized trials across eligible refractory epilepsy populations. CBD was used as adjunctive treatment rather than monotherapy. The broader review also included non-CBD cannabis derivatives and synthetic analogs.

02

What happens outside randomized trials?

Open-label, expanded-access, and retrospective studies show how CBD performed in broader clinical care. They can reveal durability and tolerability, but they cannot separate treatment effects from placebo effects or other changes in care.

Study details

Cannabidiol in patients with treatment-resistant epilepsy: an open-label interventional trial.

PubMed 26724101

Study type: open-label expanded-access trial
Population: 137 children and young adults with severe treatment-resistant epilepsy in the efficacy analysis
Formulation: oral cannabidiol
Dose: 2-5 mg/kg/day titrated up to 25 or 50 mg/kg/day
Duration: 12 weeks

Measured outcomes

Improvement reported

monthly motor-seizure frequency

Median reduction 36.5% (IQR 0-64.7); baseline median 30.0 monthly seizures and treatment-period median 15.8. ^source

Keep in mind: The study was open label and had no placebo comparator. CBD was added to existing antiseizure treatment. The efficacy analysis included 137 of 214 enrolled patients.

Study details

Real-world evidence on the use of cannabidiol for the treatment of drug resistant epilepsy not related to Lennox-Gastaut syndrome, Dravet syndrome or Tuberous Sclerosis Complex.

PubMed 37769547

Study type: multicenter retrospective study
Population: 78 patients older than 2 years with drug-resistant epilepsy of varied etiologies
Formulation: highly purified CBD
Duration: median 14 months

Measured outcomes

Improvement reported

seizure frequency

Mean seizure reduction was 67.8%; 68.8% had at least a 50% reduction at the last available visit. ^source

Keep in mind: The study was retrospective and had no placebo comparator. The population included varied epilepsy etiologies. Patients used a median of three concomitant antiseizure drugs.

Study details

Retrospective Multicenter Chart Review Study of Adjunctive Cannabidiol for Seizures Associated with Lennox-Gastaut Syndrome, Dravet Syndrome and Tuberous Sclerosis Complex.

PubMed 40650804

Study type: multicenter retrospective chart review
Population: 202 patients with Lennox-Gastaut syndrome, Dravet syndrome, or TSC-associated epilepsy
Formulation: Epidyolex 100 mg/mL oral solution
Dose: median target 11.1 mg/kg/day
Duration: up to 12 months

Measured outcomes

Improvement reported

monthly seizure days

Median seizure days per month decreased from 30 to 18 (P<0.001). ^source

Keep in mind: The study was retrospective and had no placebo comparator. CBD was used as adjunctive treatment. The population combined three epilepsy syndromes.

Study details

Effectiveness and tolerability of cannabidiol in paediatric epilepsy: a one-year multisite prospective study.

PubMed 42161151

Study type: multisite prospective open-label observational study
Population: 103 pediatric epilepsy patients in an Australian compassionate-access scheme
Formulation: purified cannabidiol added to existing care
Dose: not stated in the PubMed abstract
Duration: 12 months
Comparator: none; baseline and continuing-patient comparison; none

Measured outcomes

Improvement reported

12-month clinician-rated overall improvement among continuing pediatric patients

Among participants still receiving CBD, 40% were rated at least "much improved" at 12 months. ⁷

Safety or tolerability finding

treatment discontinuation before 12 months

Forty-six percent discontinued before 12 months, mainly for lack of effectiveness (31 patients) or adverse events (7 patients). ⁷

Keep in mind: The study was open label and had no placebo group. The 40% estimate applies only to patients who continued treatment. Clinical improvement included multiple measures and does not isolate seizure frequency alone.

Study details

Adjunctive cannabidiol in intractable pediatric epilepsy: A retrospective study on tolerability, efficacy, and safety across genetic and nongenetic etiologies.

PubMed 41630268

Study type: retrospective cohort study
Population: 29 patients aged 6 to 24 years with pediatric-onset intractable epilepsy
Formulation: adjunctive cannabidiol
Dose: median maintenance dose 14.2 mg/kg/day
Duration: median follow-up 14.3 months
Comparator: none; baseline comparison; none

Measured outcomes

Improvement reported

12-month at-least-50-percent seizure-response frequency in pediatric intractable epilepsy

At 12 months, 79.3% achieved at least 50% seizure reduction, 34.5% achieved at least 75%, and one patient became seizure-free. ^source

Safety or tolerability finding

adverse-event frequency in pediatric intractable epilepsy

Adverse events occurred in 37.9%; three patients discontinued for pneumonia, lethargy, or seizure aggravation. ^source

Keep in mind: The cohort included 29 patients and no placebo group. Etiologies were highly heterogeneous and 41.4% were unidentified. Patients used a median of five other antiseizure medications.

Study details

Long-term efficacy and safety of cannabidiol in patients with treatment-resistant focal epilepsies treated in the Expanded Access Program.

PubMed 40673944

Study type: open-label expanded-access follow-up
Population: 140 patients with treatment-resistant focal epilepsies, including 33 with TSC
Formulation: highly purified Epidiolex 100 mg/mL oral solution
Dose: started at 2-10 mg/kg/day and titrated up to 25-50 mg/kg/day
Duration: up to 144 weeks
Comparator: none; baseline comparison; none

Measured outcomes

Improvement reported

focal-seizure frequency during long-term expanded access

Median focal-seizure reductions ranged from 51% to 87% in TSC and 46% to 75% in non-TSC focal epilepsy across follow-up intervals. ⁹

Safety or tolerability finding

adverse-event frequency in focal expanded access

Adverse events occurred in 91% of the TSC group and 96% of the non-TSC group. ⁹

Keep in mind: The expanded-access study was open label and had no placebo group. Reported ranges span multiple follow-up intervals rather than one fixed endpoint. Dose was individualized and patients had varied focal epilepsy etiologies.

Study details

A multicenter study on the use of purified cannabidiol for children with treatment-resistant developmental and epileptic encephalopathies.

PubMed 40669175

Study type: descriptive real-world multicenter study
Population: 551 children with treatment-resistant developmental and epileptic encephalopathies
Formulation: purified CBD added to existing treatment
Dose: not stated in the PubMed abstract
Duration: 12 to 32 months; median follow-up 22 months
Comparator: none; baseline comparison; none

Measured outcomes

Improvement reported

long-term at-least-50-percent seizure response in pediatric DEEs

At 12 to 32 months, 50.6% had greater than 50% seizure reduction and 14.2% were seizure-free. ¹⁰

Safety or tolerability finding

adverse-event frequency in a large pediatric DEE cohort

Adverse events occurred in 32.7% and were described as mostly mild, transient, and responsive to dose adjustment. ¹⁰

Keep in mind: The study was descriptive and had no placebo group. The cohort included diverse structural, genetic, immune, infectious, and unknown etiologies. The abstract does not state dose or concomitant medication details.

Study details

Assessing Real World Efficacy, Safety, and 18-Month Retention Rates of Cannabidiol in Individuals With Drug Resistant Epilepsies.

PubMed 40968578

Study type: prospective real-world cohort using caregiver questionnaires
Population: 103 pediatric patients with labeled and off-label drug-resistant epilepsies
Formulation: highly purified Epidiolex
Dose: not stated in the PubMed abstract
Duration: 6-month outcome surveys with 18-month retention follow-up; 18 months
Comparator: none; prior-clinic-visit comparison; none

Measured outcomes

Improvement reported

caregiver-reported early seizure improvement in drug-resistant epilepsy

Caregivers reported improvement in 54% at month 1 and 48% during months 2 to 6. ^source

Improvement reported

treatment retention over 18 months

Retention declined from 97% at month 1 to 55% at month 18. ^source

Keep in mind: Seizure change was caregiver-reported without a placebo group. The cohort combined approved and off-label epilepsy indications. Questionnaires compared with prior visits and may be affected by recall and expectancy.

Study details

Adjunctive use of cannabidiol in pediatric drug-resistant epilepsy: A retrospective multicenter analysis.

PubMed 40288063

Study type: retrospective multicenter chart review
Population: pediatric drug-resistant epilepsy across five diagnostic categories
Formulation: adjunctive CBD; product details not stated in the PubMed abstract
Dose: not stated in the PubMed abstract
Duration: minimum follow-up 3 months
Comparator: none; baseline comparison

Measured outcomes

Improvement reported

median seizure frequency across pediatric drug-resistant epilepsy categories

Median seizure frequency decreased from 30 at baseline to 8 after treatment (P<.001). ^source

Keep in mind: The study was retrospective and had no placebo group. The abstract does not state sample size, dose, or detailed formulation. The cohort combined focal, generalized, LGS, DS, and other DEEs.

03

What about other and rarer epilepsies?

Newer studies report results in CDKL5 deficiency disorder, epileptic spasms, developmental epileptic encephalopathies, monogenic epilepsies, focal epilepsy, and chromosome 15 syndromes. Most of this evidence is uncontrolled.

Study details

Real-world effectiveness of highly purified cannabidiol in epilepsy associated with 15q11.2-q13.1 duplication and deletion syndromes: A multicenter study.

PubMed 41992447

Study type: multicenter retrospective real-world study
Population: 22 patients with 15q11.2-q13.1 duplication or deletion syndromes
Formulation: highly purified cannabidiol
Dose: not stated in the PubMed abstract
Duration: median follow-up 21 months
Comparator: none; baseline comparison

Measured outcomes

Improvement reported

at-least-50-percent seizure-response frequency in 15q syndromes

At last observation, 63.6% achieved at least 50% seizure reduction, 40.9% achieved at least 75%, and 18.2% were seizure-free. ^source

Keep in mind: The retrospective study included 22 patients and no placebo group. The cohort combined duplication and deletion syndromes with different seizure profiles. Most duplication-syndrome patients and two Angelman patients had a Lennox-Gastaut phenotype.

Study details

Highly purified cannabidiol (CBD) in CDKL5 deficiency disorder (CDD): Open-label prospective study.

PubMed 41677102

Study type: prospective open-label single-center study
Population: 9 female patients with CDKL5 deficiency disorder aged 1 to 24 years
Formulation: highly purified cannabidiol added to usual medicines
Dose: median 15.6 mg/kg/day
Duration: 12 months
Comparator: none; baseline comparison

Measured outcomes

Improvement reported

at-least-50-percent seizure response in CDKL5 deficiency disorder

At least 50% seizure reduction occurred in 8/9 at month 3, 6/9 at month 6, and 1/8 at month 12. ^source

Keep in mind: The study included nine patients and no placebo group. The responder rate declined substantially by 12 months. The findings apply to CDKL5 deficiency disorder and may not generalize to other epilepsies.

Study details

Cannabidiol as Adjunctive Treatment in Drug-Resistant Epilepsy With Epileptic Spasms Beyond Two Years of Age.

PubMed 41197417

Study type: retrospective longitudinal study
Population: 53 children older than 2 years with drug-resistant epileptic spasms
Formulation: purified CBD (Epidyolex) added to existing treatment
Dose: not stated in the PubMed abstract
Duration: treated from 2020 to 2024; patient-level duration not stated
Comparator: none; baseline comparison; none

Measured outcomes

Improvement reported

at-least-50-percent epileptic-spasm response after age two

Fifty-eight and one-half percent achieved at least 50% spasm reduction; 15% of responders attained complete spasm freedom. ^source

Safety or tolerability finding

adverse-event frequency in childhood epileptic spasms

Adverse events occurred in 62.2%; 11.3% discontinued because of adverse events and 17% for lack of efficacy. ^source

Keep in mind: The retrospective study had no placebo group. All patients were older than two and had epileptic spasms as the primary seizure type. Clobazam was used by 77.3%, so CBD-only attribution is not possible.

Study details

Real-world efficacy and safety of cannabidiol in developmental and epileptic encephalopathies.

PubMed 41165013

Study type: retrospective real-world cohort study
Population: 107 patients with developmental and epileptic encephalopathies
Formulation: highly purified CBD added to existing treatment
Dose: not stated in the PubMed abstract
Duration: median follow-up 20 months
Comparator: none; baseline comparison; none

Measured outcomes

Improvement reported

at-least-50-percent seizure-response frequency in developmental epileptic encephalopathies

At median 20-month follow-up, 69% achieved at least 50% seizure reduction and 21% achieved at least 75%. ^source

Safety or tolerability finding

adverse-event frequency in developmental epileptic encephalopathies

Adverse events occurred in 33.6%, and 9% discontinued because of side effects. ^source

Keep in mind: The study was retrospective and had no placebo group. The cohort combined LGS, DS, TSC, and other DEEs. Concomitant valproate and other treatments may affect outcomes.

Study details

Expanding the therapeutic role of highly purified cannabidiol in monogenic epilepsies: A multicenter real-world study.

PubMed 40126049

Study type: retrospective multicenter real-world study
Population: 266 patients across 77 monogenic epilepsies
Formulation: highly purified cannabidiol
Dose: not stated in the PubMed abstract
Duration: median follow-up 17 months
Comparator: none; baseline comparison

Measured outcomes

Improvement reported

at-least-50-percent seizure response in monogenic epilepsies

At last follow-up, 47.5% achieved at least 50% seizure reduction and 7.4% achieved seizure freedom; mean reduction was 38.6%. ^source

Keep in mind: The study was retrospective and had no placebo group. The cohort included 77 different monogenic epilepsies. Subgroup associations were exploratory and susceptible to multiple comparisons.

Study details

Real-world experience of cannabidiol in conjunction with clobazam for the treatment of seizures associated with Lennox-Gastaut syndrome and Dravet syndrome: Results from a retrospective multicentre chart review in Germany.

PubMed 40073826

Study type: retrospective multicenter chart review
Population: 126 patients with LGS or DS receiving CBD with clobazam
Formulation: Epidyolex 100 mg/mL highly purified CBD with concomitant clobazam
Dose: median target CBD dose 11.1 mg/kg/day
Duration: 12 months
Comparator: none; baseline comparison; none

Measured outcomes

Improvement reported

at-least-50-percent total-seizure response with concomitant clobazam

At least 50% total-seizure reduction occurred in 47.5% at month 3 and 45.5% at month 12. ¹²

Safety or tolerability finding

sedation frequency with concomitant clobazam

Sedation occurred in 30 patients (23.8%); diarrhea occurred in 13 (10.3%). ¹²

Keep in mind: The retrospective study had no placebo group. All patients received concomitant clobazam and other antiseizure medications. The cohort combined LGS and DS across pediatric and adult age groups.

Study details

Caregiver-reported non-seizure and seizure outcomes with cannabidiol and clobazam in patients aged ≥2 years with Lennox-Gastaut syndrome or Dravet syndrome: A subgroup analysis of the BECOME survey.

PubMed 40354745

Study type: caregiver survey subgroup analysis
Population: 243 patients with LGS or DS taking CBD with clobazam
Formulation: Epidiolex 100 mg/mL CBD oral solution with concomitant clobazam
Dose: median 14 mg/kg/day CBD plus median four other antiseizure medications
Duration: at least 3 months
Comparator: none; caregiver recall of pre-CBD status

Measured outcomes

Improvement reported

caregiver-reported seizure frequency with concomitant clobazam

Caregivers reported improved seizure frequency in 87%, severity in 81%, and net improvement in seizure-free days across seizure types in 68%. ^source

Keep in mind: The survey had no untreated or placebo comparator. Outcomes were caregiver-reported retrospectively relative to pre-CBD status. All patients used concomitant clobazam and a median of four other antiseizure medications.

04

How do reviews and formulations change the answer?

Reviews combine studies with different designs and epilepsy types. A CBD-enriched cannabis oil study is shown separately because it did not test isolated purified CBD.

Study details

A systematic review of highly purified cannabidiol in developmental and epileptic encephalopathies and complex treatment-resistant epilepsies: Changes in seizure frequency and adverse events.

PubMed 41558068

Study type: systematic literature review with narrative synthesis
Population: 57 studies, 37 DEEs or complex treatment-resistant epilepsies, and 971 patients
Formulation: highly purified plant-derived CBD oral solution
Dose: varied across included studies
Duration: varied across included studies
Comparator: varied; most evidence was uncontrolled

Measured outcomes

Improvement reported

seizure frequency in DEEs and complex treatment-resistant epilepsies beyond established indications

Forty-seven studies reported seizure reduction in at least one patient; reported thresholds and reductions varied widely. ⁸

Keep in mind: Thirty-three of the 57 studies were case reports or small case series. Definitions, response thresholds, epilepsy types, and follow-up varied widely. A narrative count of studies with at least one responder is not a pooled treatment effect.

Study details

Efficacy and safety of cannabidiol in children with developmental and epileptic encephalopathies: A systematic review.

PubMed 41135306

Study type: systematic review of all study designs
Population: 14 studies involving 682 children with developmental and epileptic encephalopathies
Formulation: pharmaceutical cannabidiol
Dose: up to 50 mg/kg/day
Duration: varied across included studies
Comparator: varied; included nonrandomized studies

Measured outcomes

Improvement reported

at-least-50-percent seizure response across pediatric DEE studies

Eleven studies reported at least 20% of participants achieved a seizure-frequency reduction of 50% or more. ^source

Safety or tolerability finding

adverse-event frequency across pediatric DEE studies

Adverse events were described as relatively common, including somnolence, appetite loss, diarrhea, fatigue, and elevated aminotransferases. ^source

Keep in mind: The review included all study designs rather than only randomized trials. The summarized threshold does not provide one pooled responder rate. Epilepsy syndromes, doses, follow-up, and risk of bias varied.

Study details

National Multicenter Cohort Study: Adjunctive Cannabidiol-Enriched Cannabis Oil for Pediatric Drug-Resistant Epilepsy Treatment in Thailand.

PubMed 40460512

Study type: prospective observational multicenter cohort
Population: 101 pediatric drug-resistant epilepsy patients across 19 Thai hospitals
Formulation: medical-grade CBD-enriched cannabis oil
Dose: median modal CBD dose 6 mg/kg/day; effective range 1-15 mg/kg/day
Duration: median follow-up 15 months
Comparator: none

Measured outcomes

Safety or tolerability finding

adverse-event frequency with CBD-enriched cannabis oil

Adverse events were reported in 92%, mostly mild; 33 discontinued, including 57% of discontinuers for intolerable adverse events. ¹¹

Keep in mind: The formulation was CBD-enriched cannabis oil, not isolated pharmaceutical CBD. The study had no placebo group. The 57% figure applies to the 33 discontinuers, not the full cohort.

How strong is the research?

Not every study answers the same question

This page separates research in people, research reviews, and earlier-stage biology before interpreting the larger question.

24 sources

Human studies

Research involving people is closest to everyday health questions. The product, dose, population, and outcome still determine what each study can show.

20 sources

Reviews and evidence summaries

Reviews can compare several studies at once. Their conclusion is only as strong and as relevant as the studies they include.

1 source

Lab, animal, and mechanism research

Early-stage research can explain biological interest. It cannot, by itself, show that the same effect happens in people.

What these studies actually looked at

The research on Does CBD reduce seizures? is not one kind of study. This source set includes 12 narrative or expert reviews, 8 clinical studies in people, 8 systematic reviews or meta-analyses, and 3 observational studies in people. ³

The recorded populations or models include people or patients (28 sources), pediatric, adolescent, or developmental context (12 sources), and 120 children and young adults with Dravet syndrome and drug-resistant seizures (1 source). A result from one group or model should not be assumed to apply to another. ⁴

The most common recorded outcome focus is seizure-related outcomes (27 sources), 12-month at-least-50-percent seizure-response frequency in pediatric intractable epilepsy (1 source), and 12-month clinician-rated overall improvement among continuing pediatric patients (1 source). Closely related outcome names can still describe different measurements. ⁵

Some source records specify doses including not stated in the PubMed abstract (8 sources), 20 mg or kg or day (4 sources), and 10 mg or kg or day (2 sources). These are descriptions of what researchers tested, not personal dosing instructions. ⁶

The Does CBD reduce seizures? source set also contains findings or reviews that remain too limited, indirect, or mixed for a broad answer. That uncertainty is part of the result, not an empty space to fill with assumptions. ⁷

Examples from the literature

What did the studies actually look at?

Each example names the research question and the study details recorded for that source.

clinical study in people

Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome.

On this page, this source examines CBD and seizure and neurodevelopmental outcomes, CBD and monthly convulsive-seizure frequency, and CBD and caregiver-rated overall condition improvement and other related questions. ¹

Study type: clinical study in people
Population or model: pediatric, adolescent, or developmental context and 120 children and young adults with Dravet syndrome and drug-resistant seizures
Outcome focus: seizure-related outcomes and monthly convulsive-seizure frequency and other recorded details
Dose recorded: 20 mg or kg or day
Evidence stage: human research

clinical study in people

Cannabidiol in patients with seizures associated with Lennox-Gastaut syndrome (GWPCARE4): a randomised, double-blind, placebo-controlled phase 3 trial.

On this page, this source examines CBD and seizure and neurodevelopmental outcomes, CBD and monthly drop-seizure frequency, and CBD and adverse-event frequency and other related questions. ²

Study type: clinical study in people
Population or model: people or patients
Outcome focus: seizure-related outcomes and monthly drop-seizure frequency and other recorded details
Dose recorded: 20 mg or kg or day
Evidence stage: human research

clinical study in people

Effect of Cannabidiol on Drop Seizures in the Lennox-Gastaut Syndrome.

On this page, this source examines CBD and seizure and neurodevelopmental outcomes and CBD and drop-seizure frequency. ³

Study type: clinical study in people
Population or model: pediatric, adolescent, or developmental context and people or patients
Outcome focus: seizure-related outcomes and drop-seizure frequency
Dose recorded: 20 mg or kg or day and 10 mg or kg or day
Evidence stage: human research

clinical study in people

Add-on Cannabidiol Treatment for Drug-Resistant Seizures in Tuberous Sclerosis Complex: A Placebo-Controlled Randomized Clinical Trial.

On this page, this source examines CBD and seizure and neurodevelopmental outcomes, CBD and tSC-associated seizure frequency, and CBD and diarrhea frequency and other related questions. ⁴

Study type: clinical study in people
Population or model: people or patients
Outcome focus: seizure-related outcomes and tSC-associated seizure frequency and other recorded details
Dose recorded: 25 mg or kg or day and 50 mg or kg or day and other recorded details
Evidence stage: human research

systematic review or meta-analysis

Cannabis derivatives and their synthetic analogs for treatment-resistant epilepsy: A systematic review and meta-analysis.

On this page, this source examines CBD and at-least-50-percent monthly seizure response at 20 mg or kg or day in randomized trials, CBD and at-least-50-percent monthly seizure response at 10 mg or kg or day in randomized trials, and CBD and serious adverse-event risk at 20 mg or kg or day in randomized trials. ⁵

Study type: systematic review or meta-analysis
Population or model: people or patients
Outcome focus: at-least-50-percent monthly seizure response at 20 mg or kg or day in randomized trials and at-least-50-percent monthly seizure response at 10 mg or kg or day in randomized trials and other recorded details
Dose recorded: 20 mg or kg or day and 10 mg or kg or day
Evidence stage: systematic review

Safety and limits

What should readers keep in mind?

Research on Does CBD reduce seizures? should be read beside safety. A compound can be non-intoxicating or naturally occurring and still have pharmacologic effects, side effects, interactions, or product-quality concerns. ²

Research doses are descriptions of what a study tested. They are not personal dosing instructions. Questions involving medications, pregnancy, children, driving, liver health, heart health, or serious symptoms deserve professional medical guidance.

Drug interactions Pregnancy and children Driving and impairment All safety topics

Common questions

Questions people ask

Yes, purified prescription CBD has reduced specific seizure types in randomized trials involving Dravet syndrome, Lennox-Gastaut syndrome, and tuberous sclerosis complex when added to other antiseizure medicines. ⁷

Does CBD work for every type of epilepsy?

No. Evidence differs by syndrome and seizure type. Research beyond the best-established syndromes is often promising but is mostly open-label or observational. ⁸

Is prescription CBD the same as store-bought CBD?

No. The strongest trials used standardized purified prescription oral CBD at weight-based doses. Consumer products can differ in formulation, dose accuracy, purity, and other ingredients. ⁹

What side effects were reported?

Studies reported effects including sleepiness or sedation, diarrhea, appetite changes, liver-enzyme elevations, adverse-event withdrawals, and medicine interactions. The exact pattern changed by dose and other medicines. ¹⁰

Keep learning

Read the research

The numbered sources below support the main overview. Links open the PubMed record or DOI in a new tab.

1
Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome. clinical study in people; human research PubMed 28538134 DOI 10.1056/nejmoa1611618
2
Cannabidiol in patients with seizures associated with Lennox-Gastaut syndrome (GWPCARE4): a randomised, double-blind, placebo-controlled phase 3 trial. clinical study in people; human research PubMed 29395273 DOI 10.1016/s0140-6736(18
3
Effect of Cannabidiol on Drop Seizures in the Lennox-Gastaut Syndrome. clinical study in people; human research PubMed 29768152 DOI 10.1056/nejmoa1714631
4
Add-on Cannabidiol Treatment for Drug-Resistant Seizures in Tuberous Sclerosis Complex: A Placebo-Controlled Randomized Clinical Trial. clinical study in people; human research PubMed 33346789 DOI 10.1001/jamaneurol.2020.4607
5
Cannabis derivatives and their synthetic analogs for treatment-resistant epilepsy: A systematic review and meta-analysis. systematic review or meta-analysis; systematic review PubMed 40267856 DOI 10.1016/j.eplepsyres.2025.107559
6
Clinically Meaningful Reduction in Drop Seizures in Patients with Lennox-Gastaut Syndrome Treated with Cannabidiol: Post Hoc Analysis of Phase 3 Clinical Trials. clinical study in people; human research PubMed 40775196 DOI 10.1007/s40263-025-01201-8
7
Effectiveness and tolerability of cannabidiol in paediatric epilepsy: a one-year multisite prospective study. observational study in people; human research PubMed 42161151 DOI 10.1016/j.yebeh.2026.111095
8
A systematic review of highly purified cannabidiol in developmental and epileptic encephalopathies and complex treatment-resistant epilepsies: Changes in seizure frequency and adverse events. narrative or expert review; systematic review PubMed 41558068 DOI 10.1016/j.eplepsyres.2026.107731
9
Long-term efficacy and safety of cannabidiol in patients with treatment-resistant focal epilepsies treated in the Expanded Access Program. open-label expanded-access follow-up; human research PubMed 40673944 DOI 10.1111/epi.18496
10
A multicenter study on the use of purified cannabidiol for children with treatment-resistant developmental and epileptic encephalopathies. descriptive real-world multicenter study; human research PubMed 40669175 DOI 10.1016/j.yebeh.2025.110590
11
National Multicenter Cohort Study: Adjunctive Cannabidiol-Enriched Cannabis Oil for Pediatric Drug-Resistant Epilepsy Treatment in Thailand. observational study in people; human research PubMed 40460512 DOI 10.1016/j.pediatrneurol.2025.04.015
12
Real-world experience of cannabidiol in conjunction with clobazam for the treatment of seizures associated with Lennox-Gastaut syndrome and Dravet syndrome: Results from a retrospective multicentre chart review in Germany. retrospective multicenter chart review; human research PubMed 40073826 DOI 10.1016/j.yebeh.2025.110302

See all 45 research sources

This complete source list is the deeper research layer for the page. Study type and evidence context are shown when they are available in the current record.

Clinical efficacy and safety of cannabidiol for pediatric refractory epilepsy indications: A systematic review and meta-analysis. systematic review or meta-analysis; evidence still limited / 1 linked research note PubMed 36206805
Consensus panel recommendations for the optimization of EPIDIOLEX® treatment for seizures associated with Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex. narrative or expert review; evidence still limited / 1 linked research note PubMed 39007525
Add-on Cannabidiol Treatment for Drug-Resistant Seizures in Tuberous Sclerosis Complex: A Placebo-Controlled Randomized Clinical Trial. clinical study in people; human research / 9 linked research notes PubMed 33346789
Highly Purified Cannabidiol for Epilepsy Treatment: A Systematic Review of Epileptic Conditions Beyond Dravet Syndrome and Lennox-Gastaut Syndrome. systematic review or meta-analysis; evidence still limited / 1 linked research note PubMed 33754312
Cannabidiol Therapy for Refractory Epilepsy and Seizure Disorders. narrative or expert review; evidence still limited / 1 linked research note PubMed 33332006
Use of cannabidiol in the treatment of epilepsy: Lennox-Gastaut syndrome, Dravet syndrome, and tuberous sclerosis complex. systematic review or meta-analysis; evidence still limited / 1 linked research note PubMed 36417631
Psychobehavioural and Cognitive Adverse Events of Anti-Seizure Medications for the Treatment of Developmental and Epileptic Encephalopathies. narrative or expert review; evidence still limited / 1 linked research note PubMed 36194365
Real-world evidence on the use of cannabidiol for the treatment of drug resistant epilepsy not related to Lennox-Gastaut syndrome, Dravet syndrome or Tuberous Sclerosis Complex. multicenter retrospective study; human research / 2 linked research notes PubMed 37769547
Retrospective Multicenter Chart Review Study of Adjunctive Cannabidiol for Seizures Associated with Lennox-Gastaut Syndrome, Dravet Syndrome and Tuberous Sclerosis Complex. multicenter retrospective chart review; human research / 2 linked research notes PubMed 40650804
Progress report on new medications for seizures and epilepsy: A summary of the 17th Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XVII). I. Drugs in preclinical and early clinical development. mechanism-focused research / 1 linked research note PubMed 39008349
CBD in the Treatment of Epilepsy. narrative or expert review; evidence still limited / 1 linked research note PubMed 38731471
Pharmacological diversity amongst approved and emerging antiseizure medications for the treatment of developmental and epileptic encephalopathies. narrative or expert review; evidence still limited / 1 linked research note PubMed 37655228
Antiseizure medications for Lennox-Gastaut Syndrome: Comprehensive review and proposed consensus treatment algorithm. narrative or expert review; evidence still limited / 1 linked research note PubMed 39854828
Cannabidiol in patients with treatment-resistant epilepsy: an open-label interventional trial. clinical study in people; open-label expanded-access trial; human research / 2 linked research notes PubMed 26724101
Cannabidiol in patients with seizures associated with Lennox-Gastaut syndrome (GWPCARE4): a randomised, double-blind, placebo-controlled phase 3 trial. clinical study in people; human research / 4 linked research notes PubMed 29395273
Comparative efficacy and safety of stiripentol, cannabidiol and fenfluramine as first-line add-on therapies for seizures in Dravet syndrome: A network meta-analysis. systematic review or meta-analysis; evidence still limited / 1 linked research note PubMed 38427284
Effect of Cannabidiol on Drop Seizures in the Lennox-Gastaut Syndrome. clinical study in people; human research / 3 linked research notes PubMed 29768152
Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome. clinical study in people; human research / 4 linked research notes PubMed 28538134
State-of-the-art management of Dravet syndrome. narrative or expert review; evidence still limited / 1 linked research note PubMed 40836583
Randomized, dose-ranging safety trial of cannabidiol in Dravet syndrome. clinical study in people; mechanism-focused research; human research / 4 linked research notes PubMed 29540584
Pharmacotherapy for Dravet Syndrome: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials. systematic review or meta-analysis; evidence still limited / 1 linked research note PubMed 37695433
Long-term safety and effectiveness of fenfluramine in children and adults with Dravet syndrome. clinical study in people; evidence still limited / 1 linked research note PubMed 40072476
Treatment of Dravet Syndrome. narrative or expert review; evidence still limited / 1 linked research note PubMed 27264138
Current and emerging pharmacotherapies in Lennox-Gastaut syndrome. narrative or expert review; evidence still limited / 1 linked research note PubMed 40468679
Anti-seizure medications for Lennox-Gastaut syndrome. systematic review or meta-analysis; evidence still limited / 1 linked research note PubMed 33825230
Lennox-Gastaut syndrome: New treatments and treatments under investigation. narrative or expert review; evidence still limited / 1 linked research note PubMed 32409177
Management of Lennox-Gastaut syndrome beyond childhood: A comprehensive review. narrative or expert review; evidence still limited / 1 linked research note PubMed 33243685
Effectiveness and tolerability of cannabidiol in paediatric epilepsy: a one-year multisite prospective study. observational study in people; human research / 2 linked research notes PubMed 42161151
Real-world effectiveness of highly purified cannabidiol in epilepsy associated with 15q11.2-q13.1 duplication and deletion syndromes: A multicenter study. multicenter retrospective real-world study; human research / 1 linked research note PubMed 41992447
Highly purified cannabidiol (CBD) in CDKL5 deficiency disorder (CDD): Open-label prospective study. prospective open-label single-center study; human research / 1 linked research note PubMed 41677102
A systematic review of highly purified cannabidiol in developmental and epileptic encephalopathies and complex treatment-resistant epilepsies: Changes in seizure frequency and adverse events. narrative or expert review; systematic review / 1 linked research note PubMed 41558068
Adjunctive cannabidiol in intractable pediatric epilepsy: A retrospective study on tolerability, efficacy, and safety across genetic and nongenetic etiologies. retrospective cohort study; human research / 2 linked research notes PubMed 41630268
Cannabidiol as Adjunctive Treatment in Drug-Resistant Epilepsy With Epileptic Spasms Beyond Two Years of Age. retrospective longitudinal study; human research / 2 linked research notes PubMed 41197417
Real-world efficacy and safety of cannabidiol in developmental and epileptic encephalopathies. retrospective real-world cohort study; human research / 2 linked research notes PubMed 41165013
Efficacy and safety of cannabidiol in children with developmental and epileptic encephalopathies: A systematic review. systematic review or meta-analysis; systematic review / 2 linked research notes PubMed 41135306
Clinically Meaningful Reduction in Drop Seizures in Patients with Lennox-Gastaut Syndrome Treated with Cannabidiol: Post Hoc Analysis of Phase 3 Clinical Trials. clinical study in people; human research / 1 linked research note PubMed 40775196
Long-term efficacy and safety of cannabidiol in patients with treatment-resistant focal epilepsies treated in the Expanded Access Program. open-label expanded-access follow-up; human research / 2 linked research notes PubMed 40673944
A multicenter study on the use of purified cannabidiol for children with treatment-resistant developmental and epileptic encephalopathies. descriptive real-world multicenter study; human research / 2 linked research notes PubMed 40669175
Assessing Real World Efficacy, Safety, and 18-Month Retention Rates of Cannabidiol in Individuals With Drug Resistant Epilepsies. prospective real-world cohort using caregiver questionnaires; human research / 2 linked research notes PubMed 40968578
National Multicenter Cohort Study: Adjunctive Cannabidiol-Enriched Cannabis Oil for Pediatric Drug-Resistant Epilepsy Treatment in Thailand. observational study in people; human research / 1 linked research note PubMed 40460512
Caregiver-reported non-seizure and seizure outcomes with cannabidiol and clobazam in patients aged ≥2 years with Lennox-Gastaut syndrome or Dravet syndrome: A subgroup analysis of the BECOME survey. observational study in people; human research / 1 linked research note PubMed 40354745
Adjunctive use of cannabidiol in pediatric drug-resistant epilepsy: A retrospective multicenter analysis. retrospective multicenter chart review; human research / 1 linked research note PubMed 40288063
Cannabis derivatives and their synthetic analogs for treatment-resistant epilepsy: A systematic review and meta-analysis. systematic review or meta-analysis; systematic review / 3 linked research notes PubMed 40267856
Expanding the therapeutic role of highly purified cannabidiol in monogenic epilepsies: A multicenter real-world study. retrospective multicenter real-world study; human research / 1 linked research note PubMed 40126049
Real-world experience of cannabidiol in conjunction with clobazam for the treatment of seizures associated with Lennox-Gastaut syndrome and Dravet syndrome: Results from a retrospective multicentre chart review in Germany. retrospective multicenter chart review; human research / 2 linked research notes PubMed 40073826

What is the bottom line?

Want the quick path or the full picture?

What to know first

What do you want to know about CBD and seizures?

Which epilepsies have the strongest evidence?

What about other seizure disorders?

How much improvement was reported?

What changes the answer?

What researchers studied about CBD and seizures

Dravet syndrome

Lennox-Gastaut syndrome

Tuberous sclerosis complex

Other and rarer epilepsies

What did the CBD seizure studies report?

Where is the strongest evidence?

monthly convulsive-seizure frequency

caregiver-rated overall condition improvement

nonconvulsive-seizure frequency

monthly drop-seizure frequency

adverse-event frequency

withdrawal due to adverse events

drop-seizure frequency

drop-seizure frequency

TSC-associated seizure frequency

TSC-associated seizure frequency

diarrhea frequency

diarrhea frequency

somnolence frequency

somnolence frequency

treatment discontinuation due to adverse events

elevated liver transaminase frequency

CBD and metabolite exposure as CBD dose increases

N-desmethylclobazam exposure

adverse-event frequency

drop-seizure reduction associated with slight-or-better caregiver improvement

at-least-50-percent monthly seizure response at 20 mg/kg/day in randomized trials

at-least-50-percent monthly seizure response at 10 mg/kg/day in randomized trials

serious adverse-event risk at 20 mg/kg/day in randomized trials

What happens outside randomized trials?

monthly motor-seizure frequency

seizure frequency

monthly seizure days

12-month clinician-rated overall improvement among continuing pediatric patients

treatment discontinuation before 12 months

12-month at-least-50-percent seizure-response frequency in pediatric intractable epilepsy

adverse-event frequency in pediatric intractable epilepsy

focal-seizure frequency during long-term expanded access

adverse-event frequency in focal expanded access

long-term at-least-50-percent seizure response in pediatric DEEs

adverse-event frequency in a large pediatric DEE cohort

caregiver-reported early seizure improvement in drug-resistant epilepsy

treatment retention over 18 months

median seizure frequency across pediatric drug-resistant epilepsy categories

What about other and rarer epilepsies?

at-least-50-percent seizure-response frequency in 15q syndromes

at-least-50-percent seizure response in CDKL5 deficiency disorder

at-least-50-percent epileptic-spasm response after age two

adverse-event frequency in childhood epileptic spasms

at-least-50-percent seizure-response frequency in developmental epileptic encephalopathies

adverse-event frequency in developmental epileptic encephalopathies

at-least-50-percent seizure response in monogenic epilepsies

at-least-50-percent total-seizure response with concomitant clobazam

sedation frequency with concomitant clobazam

caregiver-reported seizure frequency with concomitant clobazam

How do reviews and formulations change the answer?

seizure frequency in DEEs and complex treatment-resistant epilepsies beyond established indications

at-least-50-percent seizure response across pediatric DEE studies

adverse-event frequency across pediatric DEE studies

adverse-event frequency with CBD-enriched cannabis oil

Not every study answers the same question

Human studies

Reviews and evidence summaries

Lab, animal, and mechanism research

What these studies actually looked at

What did the studies actually look at?

Trial of Cannabidiol for Drug-Resistant Seizures in the Dravet Syndrome.

Cannabidiol in patients with seizures associated with Lennox-Gastaut syndrome (GWPCARE4): a randomised, double-blind, placebo-controlled phase 3 trial.

Effect of Cannabidiol on Drop Seizures in the Lennox-Gastaut Syndrome.

Add-on Cannabidiol Treatment for Drug-Resistant Seizures in Tuberous Sclerosis Complex: A Placebo-Controlled Randomized Clinical Trial.

Cannabis derivatives and their synthetic analogs for treatment-resistant epilepsy: A systematic review and meta-analysis.