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Medical Marijuana for Epilepsy: What Does the Research Say?

By Alexander Beadle

Published: Aug 12, 2019   
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According to statistics released by the US Centers for Disease Control and Prevention, there are currently around three million adults and nearly half a million children living with some form of active epilepsy in the United States. 

Around 1 in 26 people will develop the condition at some point in their lives, making epilepsy the fourth most common neurological condition in the world, behind only migraine, stroke, and Alzheimer’s disease. Globally, there is estimated to be around 50 million people living with an active epilepsy diagnosis.

People with epilepsy suffer from episodes of abnormal brain activity which disrupt the usual function of the brain, resulting in seizures. The exact nature and frequency of these seizures can vary hugely between different forms of epilepsy, as can the success rate of treatment for these seizures.

While epilepsy is a lifelong condition, for most people the symptoms of epilepsy can be easily controlled through anti-epileptic medications, meaning that the majority of suffers can go on to lead a relatively normal life. In fact, it is even possible for epilepsy to naturally go into remission; in children with absence epilepsy it is relatively common for the child to “grow out of it” as they reach puberty. 

But for up to a third of epilepsy patients, anti-epileptic medication fails to bring their seizures under control. This is known as refractory epilepsy, or intractable epilepsy. 

Medical cannabis has been floated as a potential treatment for people with refractory epilepsy. Indeed, a cannabis-derived medicine is approved by the US Food and Drug Administration for the treatment of two types of refractory epilepsy, Dravet syndrome and Lennox-Gastaut syndrome. Refractory epilepsy is also one of the conditions for which specialists in the United Kingdom are allowed to prescribe medical cannabis, though this is still rare in practice. 

But is cannabis really an effective treatment for epileptic seizures? The scientific evidence is perhaps a little murkier than you might expect.

Major review concludes “insufficient evidence” cannabis is effective

In 2017, the National Academies of Sciences, Engineering, and Medicine released a comprehensive report on the health effects of cannabis and cannabinoids, which sought to evaluate the current state of medical cannabis research with respect to a range of different medical conditions. 

The reviewers identified two systematic reviews of randomized trials and two case studies dealing with the effect of cannabinoids on epilepsy symptomology. Contrary to what we hear today, the reviewers concluded that there was “insufficient evidence to support or refute the conclusion that cannabinoids are an effective treatment for epilepsy.” 

In fact, across the more than one hundred conclusions that the report authors investigated, only three were deemed to conclusively have enough evidence to support the therapeutic use of cannabis: in reducing nausea in chemotherapy patients, treating chronic pain, and reducing muscle spasms in people with multiple sclerosis. 

The report’s conclusion on epilepsy was criticized at the time. Orrin Devinsky, director of the epilepsy center at the New York University Langone Medical Center told the Guardian that the conclusions of the entire report were broadly “conservative” and that the conclusions on epilepsy were “wrong.” 

“I think when they do a scientific review they should incorporate all the evidence that is out there for that disorder, and I don’t think they did that for epilepsy,” said Devinsky. Though he did also say that the report was still “very valuable” despite its supposed conservative nature. 

More recent cannabis and epilepsy studies show promise

Since the publishing of the 2017 review, research into cannabis and its effectiveness in treating epilepsy has continued. 

One recent study found that the cannabinoid cannabidiol (CBD) appears to be helpful in treating epileptic seizures in children. The researchers observed that for children with Lennox-Gastaut syndrome and dissociative seizures, those given a treatment of oral CBD experienced a significant reduction in the frequency of their seizures compared to those taking a placebo; nearly 40 percent of those taking CBD had their seizure frequency reduced by 50 percent or more.

However, alongside this observation, the researchers also noted that the children taking oral doses of CBD began to experience negative side effects; 8.9 percent of the CBD patients withdrew from the study because of these effects, most commonly diarrhea. Although adverse events were experienced in 87.9 percent of those treated with CBD, importantly, 72.2 percent of those taking a placebo also reported similar symptoms, raising doubts as to whether the CBD was the cause of these side effects.

Separately, a recent evaluation of combination CBD and tetrahydrocannabinol (THC) cannabis oil also saw a significant drop in seizure frequency among children with Dravet syndrome, with seizure frequency reduced by an average of 70 percent over the course of the 20-week study period. Once again, there were some negative adverse effects observed, most commonly fatigue, anorexia, and diarrhea, but this time no participants chose to withdraw from the study. The researchers believe that this study could form the basis of safe dosage guidelines should cannabis oil continue to become a common treatment for epilepsy.

Cannabis and epilepsy treatment, in the patients' own words

Cannabis’ potential as a treatment for epilepsy became central to the medical cannabis legalization movement in the United Kingdom, with the high-profile cases of two young boys, Alfie Dingley and Billy Caldwell, capturing the attention and sympathies of the British public. When the UK did eventually move to legalize the medicinal use of cannabis, the Home Secretary at the time, Sajid David, referenced the struggle of the boys in his public statement on the matter, saying that “the recent cases involving sick children made it clear to me that our position on cannabis-related medicinal products was not satisfactory.”

Hannah Deacon, the mother of Alfie Dingley, has become one of Britain’s most prominent medical cannabis campaigners following her fight to secure her son a prescription for medical cannabis. She has seen first-hand the effectiveness of cannabis oil in treating her son’s severe refractory epilepsy.

“At five, when his condition was at its worse, he was having intravenous steroids up to 25 times a month. So that's very, very dangerous,” Deacon explained to Analytical Cannabis in June. “And our doctors were saying to us that he was so seriously ill that the seizures may kill him. But if the seizures didn't, it was likely the steroids would because they can cause organ failure.” 

“So we then went to Holland in 2017, where we worked with a pediatric neurologist to use medical cannabis. And we saw [Alfie’s] seizures drop to once every 17 days, and then one seizure every 40 days. So, for us, it was like a miracle.”

Deacon has argued that patient stories like Alfie’s should be considered as viable pieces of evidence by UK regulators, which still restrict wider access to medical cannabis. It’s a sentiment shared by Peter Carroll, a medical cannabis campaign founder, who confronted a UK parliamentary panel earlier this year on the issue. 

“I think that we have to take a broader view of the evidence here because there is a point where multiple anecdotal stories do actually build on to a pattern of evidence,” he stated. “And it seems absurd to me that we have to wait three, four or five years on these trials to be produced when there are actually real-life cases now.”

A recent report from a UK health body stated that the research supporting cannabis as an epilepsy treatment is “limited and of low quality,” and so it “did not warrant a practice recommendation.”

However, a separate review from NHS England, which said children’s experiences on medicinal cannabis should be considered as evidence of how well the drug works. 

Alexander Beadle

Science Writer

Alexander Beadle has been working as a freelance science writer since 2017 and has covered the cannabis industry for Analytical Cannabis since 2018. He has also written for our sister publication, Technology Networks, and the cannabis industry consultant firm Prohibition Partners, among others. Alexander holds a Master's in Materials Chemistry from the University of St. Andrews, where he won a Chemistry Purdie scholarship, and conducted research into zeolite crystal growth mechanisms and the action of single-molecule transistors.


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