The Institute of Medicine wrote in its Mar. 17, 1999 report, "Marijuana and Medicine: Assessing the Science Base":
"Epilepsy is a chronic seizure disorder that affects about 2 million Americans and 30 million people worldwide. It is characterized by recurrent sudden attacks of altered consciousness, convulsions, or other motor activity. A seizure is the synchronized excitation of large groups of brain cells.
There are anecdotal and individual case reports that marijuana controls seizures in epileptics (reviewed in a 1997 British Medical Association report), but there is no solid evidence. While there are no studies indicating that either marijuana or THC worsen seizures, there is no scientific basis to justify such studies."
Donald Gross, MD, Assistant Professor of Neurology at the University of Alberta, et al., stated in their June 8, 2004 article, "Marijuana Use and Epilepsy; Prevalence in Patients of a Tertiary Care Epilepsy Center," published in Neurology:
"Twenty-one percent of subjects had used marijuana in the past year with the majority of active users reporting beneficial effects on seizures. Twenty-four percent of all subjects believed marijuana was an effective therapy for epilepsy.
Despite limited evidence of efficacy, many patients with epilepsy believe marijuana is an effective therapy for epilepsy and are actively using it."
Is Marijuana an Effective Treatment for Epilepsy (Seizures)?
Katherine Mortati, MD, a neurologist at the Comprehensive Epilepsy Center at SUNY Downstate Medical Center, et al., stated in their 2007 study "Marijuana: An Effective Antiepileptic Treatment in Partial Epilepsy? A Case Report and Review of the Literature," published in Reviews in Neurological Diseases:
"Although more data are needed, animal studies and clinical experience suggest that marijuana or its active constituents may have a place in the treatment of partial epilepsy.
[In the study] we present the case of a 45-year-old man with cerebral palsy and epilepsy who showed marked improvement with the use of marijuana. This case supports other anecdotal data suggesting that marijuana use may be a beneficial adjunctive treatment in some patients with epilepsy."
The British Epilepsy Association stated on its website (accessed May 3, 2006):
"There is scientific evidence to suggest that cannabis may be beneficial in treating a number of conditions, including epilepsy.... Some reports suggest that it can reduce seizures. Other reports point to an increase in seizures."
John Brust, MD, Professor of Clinical Neurology at Columbia University, et al., concluded in their 1990 study "Illicit Drug Use and the Risk of New-onset Seizures," published in the American Journal of Epidemiology:
"Marijuana use appeared to be a protective factor against first seizures in men. [...]
Marijuana contains numerous cannabinoid compounds that differ in convulsant and anticonvulsant properties. Anticonvulsant properties were first noted in the 15th century, yet studies in humans have been few. [...]
The authors conclude that heroin use is a risk factor and marijuana use a protective factor for new-onset seizures."
The American Epilepsy Society stated the following in its Feb. 28, 2014 statement titled "AES Position on Medical Marijuana," available at aesnet.org and confirmed as current in a Nov. 7, 2014 email from AES to ProCon.org:
"The recent anecdotal reports of positive effects of the marijuana derivative cannabidiol for some individuals with treatment-resistant epilepsy give reason for hope. However, we must remember that these are only anecdotal reports, and robust scientific evidence for the use of marijuana is lacking. The lack of information does not mean that marijuana is ineffective for epilepsy. It merely means that we do not know if marijuana is a safe and effective treatment for epilepsy, which is why it should be studied using the well-founded research methods that all other effective treatments for epilepsy have undergone. Such safety concerns coupled with a lack of evidence of efficacy in controlled studies result in a risk/benefit ratio that does not support use of marijuana for treatment of seizures at this time. Healthcare professionals, patients, and caregivers are reminded that use of marijuana for epilepsy may not be advisable due to this lack of information on safety and efficacy."
Robert DeLorenzo, MD, PhD, MPH, Professor of Neurology in the Virginia Commonwealth University School of Medicine, stated in a press release about his study "The Endogenous Cannabinoid System Regulates Seizure Frequency and Duration in a Model of Temporal Lobe Epilepsy," published in the Oct. 1, 2003 issue of the Journal of Pharmacology and Experimental Therapeutics:
"[I]ndividuals both here and abroad report that marijuana has been therapeutic for them in the treatment of a variety of ailments, including epilepsy. But the psychoactive side effects of marijuana make its use impractical in the treatment of epilepsy. If we can understand how marijuana works to end seizures, we may be able to develop novel drugs that might do a better job of treating epileptic seizures."
Epilepsy Ontario (Canada) stated on its website (accessed on May 3, 2006):
"Dependable documentation of the effectiveness of Cannabis sativa as an antiepileptic medication is severely limited at this time.
Some accounts show a reduction in seizure frequency and/or severity for some people with epilepsy. Whether this is due to anticonvulsant properties of cannabis or to a reduction in physical and/or psychological stress levels is not fully known and cannot be clarified without further comprehensive scientific scrutiny....
Like any drug, cannabis probably has potential to both harm and heal. Without bone-fide scientific investigation and evaluation, the efficacy of Cannabis sativa as an antiepileptic drug cannot be safely or surely ascertained....
Since THC has dual effects and there are unknown properties of marijuana, marijuana is NOT recommended for people with epilepsy.
Reliable documentation of the effectiveness of marijuana as an anti-epileptic medication is extremely limited at this time. While some accounts show a reduction in seizure frequency and/or severity in some people who have epilepsy, others suggest that marijuana may actually trigger seizures. Further investigation is needed to determine the effectiveness and side effects of cannabis as an anti-seizure drug."
Denis Petro, MD, Founding Director of Patients Out of Time, stated in his 1997 paper "Seizure Disorders" published in Cannabis in Medical Practice - A Legal, Historical and Pharmacological Overview of the Therapeutic Use of Marijuana:
"Seizures have been reported in patients after they used THC [Marinol] to control nausea in cancer chemotherapy. Since THC is psychoactive in many animal studies and is associated with other adverse effects, THC can be eliminated from consideration as a potential candidate for treatment of epilepsy.
In animal seizure models CBD [cannabidiol] has been shown to have anticonvulsant properties with potential in grand mal, cortical focal, and complex partial seizures....
In summary, a review of the literature documents some reports of the effects of marijuana in seizure disorders. The data concerning marijuana is mixed with both positive and negative reports. The scientifice evidence in support of CBC [cannabidiol] is stronger based on both preclinical and clinical studies."