A new study led by epilepsy specialists at NYU Langone Medical Center shows that some children and adults with treatment-resistant epilepsy may benefit from a treatment regimen including cannabidiol, a compound in medical marijuana that does not contain psychoactive properties.

In a multi-site study led by principal investigator Orrin Devinsky, MD, director of the NYU Langone Comprehensive Epilepsy Center, researchers saw over a 50 percent reduction in frequency of certain types of seizures in some patients taking the cannabidiol.

The findings will be presented at the American Academy of Neurology’s 67th Annual Meeting in Washington, DC, April 18 to 25, 2015.

Anecdotal reports of cannabidiol’s efficacy for epilepsy have been widely reported in media, leading some families to move to areas of the country where medical marijuana has been legalized. But until now, the compound has rarely been studied scientifically, notes Dr. Devinsky.

"Seizures that don’t respond to medication or surgical treatments can be devastating for sufferers and their families," says Dr. Devinsky, a professor in the Departments of Neurology, Neurosurgery, and Psychiatry at NYU Langone. "Trials like ours are crucial to helping families know whether a compound like cannabidiol might provide safe and effective help."

The new study included 213 participants between 2 and 42 years old (median age 11 years), and took place at 10 U.S. centers that were granted FDA-approved open-label Expanded Access, including NYU Langone. Patients qualifying for the study had to have a treatment-resistant epileptic condition, such as Lennox-Gastaut and Dravet syndromes.

All patients were prescribed cannabidiol in a liquid daily dose that was gradually increased up to a potential maximum of 25mg/kg over 12 weeks. For the 137 patients who completed the study, the number of seizures decreased by an average of 54 percent throughout the 12-week period.

In particular, among 23 patients with Dravet syndrome who completed the study, convulsive seizures reduced by 53 percent. The 11 patients with Lennox-Gastaut Syndrome who finished the study reported a 55 percent reduction in the number of atonic or "drop" seizures, which cause muscles to go limp.

Twelve people, or 6 percent of the participants, stopped taking the drug due to side effects. Of those that remained in the study, side effects included drowsiness (21 percent), diarrhea (17 percent), fatigue (17 percent), and decreased appetite (16 percent).

About 5.1 million people in the United States have been diagnosed with epilepsy, according to the Centers for Disease Control and Prevention. About one-third of them have seizures that cannot be controlled by medication. Severe forms of epilepsy, such as Lennox-Gastaut syndrome and Dravet syndrome, are marked by frequent, treatment-resistant seizures.

The study was an open-label trial, meaning both patients and researchers knew they were receiving the cannabidiol drug. Future research will be in the form of randomized, placebo-controlled trials, which often eliminates the possibility of a placebo effect.

"Though the early results are promising, we still have a lot more to find out about cannabidiol, from the proper dosing regimens to which patients might benefit more than others," says Dr. Devinsky. "In this national climate of increased acceptance towards medical marijuana, it is crucial that scientifically-validated research, not policy, guides patient care."

GW Pharmaceuticals in the U.K. supported the study and supplied the cannabidiol.

Dr. Devinsky will present his findings at 6:15PM EST, on Wednesday, April 22, 2015, in Ballroom C of the Walter E. Washington Convention Center in Washington, DC.

In addition to Dr. Devinsky, the authors of this study are: Joseph Sullivan, Daniel Friedman, Elizabeth Thiele, Eric Marsh, Linda Laux, Ian Miller, Robert Flamini, Angus Wilfong, Francis Filloux, Matthew Wong, Nicole Tilton, Patricia Bruno, Judith Bluvstein, Anup Patel, and Maria Roberta Cilio.