By Frequent Users Had More Severe Seizures
A study led by WashU Medicine researchers found that adults with drug-resistant epilepsy who used cannabis most days had more than twice as many convulsive seizures per year and became resistant to antiseizure medications years sooner than nonusers. The study appears September 28 in the journal Epilepsia.
The authors examined 64 adults with drug-resistant epilepsy who were admitted to a specialized inpatient unit where doctors observe seizure activity in real time. About one-third of them reported using cannabis recreationally most days.
Among frequent users, 90% experienced the convulsive types of seizures most associated with injury and sudden unexpected death in epilepsy, often called grand mal or generalized tonic-clonic seizures. In contrast, about half of nonusers did not experience these types of seizures.
The researchers compared 22 frequent recreational cannabis users, defined as people who reported using cannabis 20 days a month or more, with 42 nonusers. The records came from patients treated between 2019 and 2024 in an epilepsy monitoring unit at the University of Wisconsin School of Medicine and Public Health.
Frequent users were seen at the inpatient epilepsy monitoring unit an average of five years after their first seizure, compared with 18 years for nonusers. They were discharged on more antiseizure medications despite having had epilepsy for far less time.
Researchers Could Not Prove Causation
The study could not determine if cannabis use was responsible for the more severe clinical findings among frequent users. The findings cannot establish that cannabis use worsens epilepsy, but there is a concerning association.
However, among 15 frequent users whose timelines could be documented, all started using cannabis before experiencing their first seizure. This weakens the likelihood that they began using cannabis in hopes of improving their epilepsy.
Frequent users’ brain scans looked largely normal, despite severe epilepsy usually leaving visible scarring on the hippocampus. Aaron F. Struck, MD, the study’s senior author, indicated this suggested something other than the usual disease process was going on.
Struck said the research was spurred by a trend he observed treating patients amid the boom in recreational cannabis use. “The one thing they had in common was frequent, high-potency cannabis use,” Struck said.
Struck said the findings make cannabis use worth raising directly with patients, especially those using it for issues such as insomnia for which more proven treatments are available.
Larger Study Is Being Designed
The team is designing a larger, multisite study including geographic regions with distinct cannabis legalization histories. Researchers plan to incorporate objective measures at admission instead of relying on patients reporting their own cannabis use.
Study first author Santiago Philibert-Rosas, MD, said frequent users showed a clear profile: patients in their 20s, mostly male, without the usual risk factors for epilepsy, whose seizures escalated quickly from onset to admission.
A purified form of cannabidiol is FDA-approved for treating some severe forms of epilepsy, but that medication contains no THC. The cannabis sold in the recreational market is increasingly high in THC and low in CBD, according to recent studies of cannabis potency.
