Researchers have published what they say is the first scientific evidence that medicinal cannabis helps children with severe epilepsy.

Key points: Research shows cannabinol is "as good as some of the best anti-epilepsy medications"

Research shows cannabinol is "as good as some of the best anti-epilepsy medications" 40 per cent of patients had their seizures halved

40 per cent of patients had their seizures halved Some side effects were reported

Regular doses of medicinal cannabis can reduce seizures in children with severe epilepsy, new research shows.

Australian doctors were part of an international trial, testing a component of medicinal cannabis known as cannabidiol in kids with Dravet syndrome.

It is a complex disorder where children suffer drug-resistant seizures and a high death rate.

One of the authors, University of Melbourne Professor Ingrid Scheffer, welcomed the findings.

"This research is critically important. It's the first scientific evidence that cannabidiol is effective for uncontrolled seizures in Dravet syndrome," she said.

"Until now, there has only been anecdotal evidence but now we have scientific evidence proving that medicinal cannabis is definitely effective in severe epilepsy."

Some side effects reported

In the study, published in the New England Journal of Medicine, cannabidiol liquid was used to treat the children.

It is a natural compound found in cannabis stalks and flowers and does not contain mind altering properties.

Patients in the study remained on epilepsy medications as well as taking either the cannabidiol liquid or a placebo.

The frequency of seizures was measured over 14 weeks.

Of those given medicinal cannabis, more than 40 per cent had their seizures halved.

Some of the patients given cannabidiol reported mild to moderate side effects such as diarrhoea, vomiting or fatigue.

"It's not a fix-all but these findings show that cannabinol is as good as some of our best anti-epilepsy medications," Professor Scheffer said.

Professor Scheffer said other Australian groups were trialling medicinal cannabis, mainly in open-label trials where patients know if they are getting the drug or the placebo.

"We are running another trial in adults with focal epilepsy, using a gel, and the anecdotal response has been very exciting," she said.

Epilepsy Action Australia chief executive Carol Ireland hoped the research would prompt authorities to fast-track processes to make cannabis more available.

"Some families I think will feel heartened by this. It's the proof of what they already knew," she said.

But she said other families may feel afraid because "they still can't, for the most part, get access to a legal product right now".

Ms Ireland said several issues needed to be addressed for families seeking medicinal cannabis, including better access to the drug, price and finding a physician to prescribe it.