A medicinal cannabis trial has shown cannabidiol significantly reduces seizures in children with a rare yet "catastrophic" form of epilepsy and can even eliminate them altogether.
Research published in The New England Journal of Medicine found five per cent of participants with Dravet syndrome were seizure-free at the end the 14 week trial.
Out of every 500 children with epilepsy, two children at most are likely to have this form of the condition that starts in infancy and is marked by frequent and often prolonged seizures.
It is a complex childhood epilepsy and in most cases medical drugs don't work to control the seizures that can result in sudden and unexpected death.
"Dravet syndrome is a catastrophic early-onset encephalopathic epilepsy, with a high mortality rate," wrote the authors of the paper.
An international team of researchers including University of Melbourne Chair of Paediatric Neurology and Austin Health Director of Paediatrics, Professor Ingrid Scheffer, studied cannabidiol - known as CBD - for the treatment of drug- resistant convulsive seizures in 120 children with Dravet syndrome from across the US and Europe.
Cannabidiol is one of at least 113 active cannabinoids identified in cannabis.
The children were randomly assigned a CBD oral solution or a placebo, in addition to standard anti-epileptic treatment for 14 weeks.
After that time, the median frequency of convulsive seizures per month decreased from 12.4 to 5.9 with cannabidiol, compared with a decrease from 14.9 to 14.1 with placebo.
Nearly a half recorded a 50 per cent drop in seizure frequency.
Side effects were, however, more frequent in the cannabidiol group and included diarrhoea, vomiting, fatigue, increased body temperature, drowsiness and abnormal liver-function tests.
"This randomised, controlled trial showed that cannabidiol resulted in a greater reduction in convulsive-seizure frequency than placebo among children and young adults with drug-resistant Dravet syndrome," wrote the authors.
Professor Scheffer says this trial is the first scientific proof cannabidiol is effective, although more research is needed to determine it's safety.
"Until now, there has only been anecdotal evidence but now we have scientific evidence proving that cannabidiol is definitely effective in severe epilepsy.
"The next question is whether cannabidiol is effective in other forms of epilepsy and it is great that there are trials already underway of cannabidiol in other groups of patients with epilepsy," Prof Scheffer said.