Frequent Cannabis Use Linked to More Severe Seizures in Epilepsy Study A Washington University study of 64 treatment-resistant epilepsy patients found frequent cannabis users had more severe seizures and faster epilepsy progression, though causation is unproven. Frequent cannabis use is associated with more severe seizures and faster worsening of epilepsy in people whose condition resists standard treatment, according to a study published by researchers at Washington University School of Medicine in St. Louis. The team examined the medical records of 64 patients admitted to an epilepsy monitoring unit at the University of Wisconsin School of Medicine and Public Health between 2019 and 2024. The findings, while not proof of cause and effect, suggest that clinical screening and prospective studies are needed to evaluate how cannabis affects seizure outcomes. Cannabis Use and Treatment-Resistant EpilepsyThe researchers were motivated by their own clinical experiences. They noticed a growing number of patients with severe epilepsy who appeared to share little in common besides frequent cannabis use. That observation prompted them to dig deeper into the medical records of people with drug-resistant epilepsy, meaning the condition had failed to respond to at least two anti-seizure medications.The inpatient epilepsy monitoring units are used to evaluate stubborn cases under close supervision and determine the best course of treatment. All told, the team studied 64 patients. Twenty-two reported frequent cannabis use, defined as using the drug at least 20 times a month, and the researchers compared them with 42 non-users.Severe Seizures More Common in UsersFrequent cannabis users were more likely to have epilepsy with focal to bilateral tonic-clonic seizures, a severe type of seizure, than non-users, at 90 percent compared to 57 percent. They also experienced these severe seizures more often and were taking more anti-seizure medications on average.It took less time for these patients to need specialized care than non-users, a sign their condition had worsened quicker. On average, frequent cannabis users were admitted to the unit five years after the onset of their epilepsy, compared to 18 years for non-users.The study is observational, so it cannot demonstrate a clear cause-and-effect link between cannabis use and epilepsy. It is also based on a small sample of patients who self-reported their level of cannabis consumption, further weakening the conclusions that can be drawn from the data. At the same time, the authors say there is enough worrying evidence to warrant further research.THC Suspected as Possible CulpritEpidiolex, a cannabis-derived medication, is used to manage certain kinds of seizures. Importantly, Epidiolex is made only from cannabidiol, or CBD, one of the two major active compounds in cannabis, and not from the other, THC. The team strongly suspects THC could be the primary culprit behind the unsettling trend.Much more THC is present in cannabis products on average than in the past. According to the authors, there is some evidence that chronic high THC use could change brain activity in ways that make severe epilepsy more likely to happen or that weaken the effectiveness of anti-seizure medications. People who use cannabis all the time might also be more likely to forget to take their medications as often, offering another possible explanation.The study also found that people who first reported using cannabis in the past decade were quicker to develop seizures afterward than those who started two or more decades ago. That is perhaps another clue that higher THC products today are to blame for this recent trend, though this finding should be viewed with caution for now due to the small number of people and the use of self-reports, the researchers wrote.More Questions Than Answers RemainThe team is now working on a larger, more proactive study that will look at a greater diversity of people with epilepsy, including from areas of the country with different patterns of cannabis legalization. They also plan to objectively measure people's cannabis use, such as through blood tests for THC.For the time being, there are still more questions than answers about the link between cannabis and epilepsy. Lead study author and WashU researcher Santiago Philibert-Rosas said in a statement from the university that the honest answer when a patient asks whether their cannabis use is affecting their seizures is that the researchers are not sure. Larger studies will help give patients a real answer, including how much matters and whether stopping helps, so they can make an informed decision.