Marijuana plants for sale are displayed at the medical marijuana farmers market in Los Angeles Thomson Reuters A medical marijuana derivative known as cannabidiol (CBD) has been proved to be effective in reducing seizure frequency in most children and young adults. A yearlong study carried out at the NYU Langone Medical Center found that there was a reduction of seizures in children and young adults by more than a third.

The study is also the first to give a clearer picture of the safety, tolerability and efficacy of prescription CBD in children and adults with treatment resistant epilepsy. Some 214 patients aged between one and 30 were given an oral CBD treatment known as Epidiolox over a 12-week period in 2014, and results showed there was an average drop of 36.5% reduction in monthly motor seizures.

The median frequency of monthly motor seizures dropped from 30 at the beginning to 15.8 over the course of the 12 weeks, according to the research which was led by Orrin Devinsky, professor of neurology, neurosurgery, and psychiatry and director of the Comprehensive Epilepsy Center at NYU Langone and published in Lancet Neurology. Furthermore, the cannabis derivative also showed a sufficient safety profile and was well endured by most patients, but there some adverse side effects such as drowsiness, decreased appetite, diarrhoea, fatigue and convulsion.

Devinsky said: "We are very encouraged by our trial results showing that CBD was safe and well-tolerated for most patients, and that seizures dropped significantly. But before we raise hopes for families who regularly deal with the devastation of treatment-resistant epilepsy, more research, including further studies through our ongoing randomized controlled trial, are needed to definitively recommend CBD as a treatment to patients with uncontrolled seizures.

"I empathize with parents who are looking for answers and will try anything to help their children suffering the devastating effects of intractable epilepsy. But we must let the science, and not anecdotal success stories and high media interest, lead this national discussion. Taking CBD in a controlled medical setting is vastly different from going to a state where medical marijuana is legal and experimenting with dosing and CBD strains."