Does cannabis affect the seizure threshold?

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Last updated: March 27, 2025 • View editorial policy

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From the Guidelines

Cannabis can lower the seizure threshold, particularly with high THC content, and its use should be approached with caution in patients with seizure disorders. When considering the impact of cannabis on seizure threshold, it's essential to differentiate between its components, primarily CBD (cannabidiol) and THC (tetrahydrocannabinol), as they have opposing effects on neuronal excitability 1. CBD has been recognized for its anticonvulsant properties, capable of raising the seizure threshold, which is the basis for its use in FDA-approved medications like Epidiolex for treating certain seizure disorders at specific doses. In contrast, THC may decrease the seizure threshold, potentially triggering seizures in susceptible individuals. The variability in effects is largely dependent on the cannabis strain's CBD:THC ratio, the dosage and frequency of use, and individual factors such as genetic predisposition and concurrent medication use.

Key Considerations

  • The CBD:THC ratio in cannabis strains significantly influences its impact on seizure threshold, with higher CBD and lower THC content being preferable for patients with epilepsy.
  • Dosage and frequency of cannabis use are critical, as higher doses or more frequent use may increase the risk of lowering the seizure threshold.
  • Individual factors, including genetic predisposition, concurrent medications, and the specific type of seizure disorder, play a significant role in how cannabis affects seizure threshold.
  • The interaction between cannabinoids and the endocannabinoid system, which modulates neuronal excitability, underlies the effects of CBD and THC on seizure threshold.

Clinical Implications

Given the potential of cannabis, particularly high THC content, to lower the seizure threshold, its use in patients with seizure disorders should be carefully considered and monitored. Patients should be advised to use cannabis under physician supervision, preferably with formulations high in CBD and low in THC. This approach can help mitigate the risks associated with cannabis use in epilepsy while potentially benefiting from its therapeutic effects. As noted in recent clinical guidelines, such as those addressing the management of adult patients presenting to the emergency department with seizures 1, the complexity of seizure management can be compounded by substance use, including cannabis, highlighting the need for cautious and informed decision-making.

From the Research

Effects of Cannabis on Seizure Threshold

  • The relationship between cannabis use and seizure threshold is complex and not fully understood 2.
  • Some evidence suggests that marijuana and its active cannabinoids have antiepileptic effects, but these may be specific to partial or tonic-clonic seizures 2.
  • In some animal models, marijuana or its constituents can lower the seizure threshold 2.
  • Cannabidiol (CBD), a non-psychoactive component of cannabis, has been shown to have anti-seizure effects in animal models and human studies 3, 4, 5, 6.
  • CBD has been found to reduce seizure frequency in patients with drug-resistant epilepsy, particularly in those with Dravet Syndrome, Lennox-Gastaut Syndrome, and seizures associated with tuberous sclerosis complex 3, 5, 6.

Mechanisms of Action

  • The exact mechanisms by which cannabis and its constituents affect seizure threshold are not fully understood, but may involve modulation of neuronal activity and inhibition of excitatory neurotransmission 4.
  • CBD has been shown to have a potent anti-seizure effect, possibly due to its ability to inhibit the release of glutamate and other excitatory neurotransmitters 3.

Clinical Implications

  • The use of cannabis and CBD as adjunctive therapy for epilepsy has been found to be effective in reducing seizure frequency and improving quality of life for some patients 5, 6.
  • However, further controlled and adequately powered studies are needed to assess the pharmacokinetics and impact of long-term use of cannabis and CBD in patients with epilepsy 5, 6.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

3
Research

Use of cannabidiol in the treatment of epilepsy.

Neurologia i neurochirurgia polska, 2022

6
Research

Cannabinoids in treatment-resistant epilepsy: A review.

Epilepsy & behavior : E&B, 2017

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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