A new study published in Neurological Research and Practice finds that off-label use of cannabidiol (CBD) in patients with various forms of refractory epilepsy can significantly reduce seizure frequency and is generally well-tolerated.

Researchers from University Hospital Bonn, Philipps-University Marburg, Goethe-University Frankfurt, and University Medicine Frankfurt conducted a retrospective analysis of 108 patients treated with CBD between 2019 and 2023 across six German epilepsy centers. The cohort included individuals with focal-onset, genetic generalized, and other unclassified epilepsies, most of whom had not responded to prior treatments.

Three months after initiating CBD therapy, nearly 39% of patients experienced at least a 50% reduction in seizures. Among those with tonic-clonic seizures, the response rate was even higher—nearly 46% saw seizure frequency drop by at least half, and 17% became seizure-free. Notably, the benefits did not appear to depend on age, sex, or concurrent use of other antiseizure medications such as clobazam.

Retention rates were high, with 85% of patients still using CBD after three months and 61% continuing treatment after one year. Improvements were also observed in overall condition and behavior, as rated by clinicians using the Clinical Global Impression scale.

Side effects were reported in 38% of patients, with diarrhea, sedation, and gastrointestinal symptoms being the most common. Despite these adverse events, the study supports CBD’s safety and effectiveness as an add-on therapy for a wider range of epilepsy types than currently approved.