Can Cannabis Treat Epileptic Seizures?

Charlotte Figi, an eight-year-old girl from Colorado with Dravet syndrome, a rare and debilitating form of epilepsy, came into the public eye in 2013 when news broke that medical marijuana was able to do what other drugs could not: dramatically reduce her seizures. A third of epilepsy sufferers, such as Charlotte, may have cannabis to treat their condition.

Last month Orrin Devinsky, a neurologist at New York University Langone Medical Center, and his colleagues across multiple research centers published the results from the largest study to date of a cannabis-based drug for treatment-resistant epilepsy in The Lancet Neurology. Researchers treated 162 patients using a CBD (99 percent) extract and kept them supervised for twelve weeks. The treatment was added to patients' current medications. All participants were aware of what was happening.

The researchers reported the intervention reduced motor seizures at a rate similar to existing drugs (a median of 36.5 percent) and 2 percent of patients became completely seizure free. The study found that 79 percent of patients experienced side effects like fatigue, sleepiness, and diarrhea. Only 3 percent were unable to continue the research due to these adverse reactions. "I was a little surprised that the overall number of side effects was quite high but it seems like most of them were not enough that the patients had to come off the medication," says Kevin Chapman, a neurology and pediatric professor at the University of Colorado School of Medicine who was not involved in the study. I think this study provides good evidence that the medication is safe. Although there were some serious side effects, they were not as severe as expected.

Stories of cannabis's abilities to alleviate seizures have been around for about 150 years but interest in medical marijuana has increased sharply in the last decade with the help of legalization campaigns. Patients and scientists alike have begun to pay more attention to CBD, the major compound in cannabis. CBD, unlike tetrahydrocannabinol(THC), isn't responsible for THC's euphoric properties. It also doesn’t cause a high or present the same risk as THC. Researchers have found that CBD can lead to addiction and cognitive impairment. Instead, research has shown CBD to be an anticonvulsant. It may also have antipsychotic qualities.

Devinsky's trial is the strongest evaluation of CBD's effects on epilepsy. Prior studies had less than 20 participants. However, many questions still remain. In a subsequent commentary published this January, also in The Lancet Neurology, Kamil Detyniecki and Lawrence Hirsch, neurologists at the Yale University School of Medicine who were not involved in the research, outlined the study's major limitations, which include possible placebo effects and drug interactions.

The trial, which was not randomized and had no control groups, raised concerns about the placebo effect. Previous studies showed that it might be stronger with cannabis-based products. Chapman's group from the University of Colorado conducted a 2015 study that showed 47 percent of those whose families moved to Colorado for treatment of their cannabis-based epilepsy reported improvements, as compared to 22 percent of people who had lived in Colorado.

Another issue is drug interactions. Because CBD can inhibit liver enzymes and increase body concentrations, it is possible for CBD to interact with other drugs. If CBD is combined with another compound, the patient may experience side effects that are more due to their increased exposure.

Both commentary authors agreed that the study was a significant step towards establishing CBD treatment as an effective and safe epilepsy medication. Detyniecki said, "This is a great first step." He says, "Despite all the adverse reactions that CBD has caused, there were not surprising side effects."

Evidence suggesting that CBD is effective against treatment-resistant epilepsy may be growing but scientists still know very little about how it works-other than the likelihood that it is "completely different than any other seizure drug we know," as Devinsky puts it. He says that this is a positive thing. However, there are some concerns.

The limitations of the current blinded, placebo-controlled trials that test CBD on Dravet and Lennox Gastaut, another form of epilepsy, are addressed by many researchers. While CBD is being investigated as an epilepsy treatment, most researchers and physicians, including the ones involved in this trial, caution against optimism.

Devinksy believes that CBD is safe if children have tried other drugs, but the severity and impact on their quality of life remains severe. "But I believe it's critical that we as a scientific society get more data." Cannabis might be the most effective treatment for epilepsy for certain people, but patients are advised to wait until scientists clear up the fog.