A medicinal liquid form of marijuana may show promise as a treatment for children with severe epilepsy that is not responding to other treatments, according to a study released today that will be presented at the American Academy of Neurology's 67th Annual Meeting in Washington, DC, April 18 to 25, 2015.

The study involved 213 people, ranging from toddlers to adults, with a median age of 11 who had severe epilepsy that did not respond to other treatments. Participants had Dravet syndrome and Lennox-Gastaut syndrome, epilepsy types that can lead to intellectual disability and lifelong seizures, as well as 10 other types of severe epilepsy.

The participants were given the drug cannabidiol, a component of marijuana that does not include the psychoactive part of the plant that creates a "high." The drug is a liquid taken daily by mouth. Participants all knew they were receiving the drug in the open-label study, which was designed to determine whether the drug was safe and tolerated well.

Researchers also measured the number of seizures participants had while taking the drug. For the 137 people who completed the 12-week study, the number of seizures decreased by an average of 54 percent from the beginning of the study to the end. Among the 23 people with Dravet syndrome who finished the study, the number of convulsive seizures had gone down by 53 percent by the end of the study. For the 11 people with Lennox-Gastaut syndrome who finished the study, there was a 55 percent reduction in the number of atonic seizures, which cause a sudden loss of muscle tone.

A total of 12 people, or 6 percent, stopped taking the drug due to side effects. Side effects that occurred in more than 10 percent of participants included drowsiness (21 percent), diarrhea (17 percent), tiredness (17 percent) and decreased appetite (16 percent).

Study author Orrin Devinsky, MD, of New York University Langone Comprehensive Epilepsy Center and a Fellow of the American Academy of Neurology, said that these are early findings and larger, placebo-controlled, double-blind trials are needed to measure the effectiveness of the drug.

"So far there have been few formal studies on this marijuana extract," Devinsky said. "These results are of great interest, especially for the children and their parents who have been searching for an answer for these debilitating seizures."

The study was supported by GW Pharmaceuticals.