Can cannabis help fight epileptic seizures in children? Some families have sworn by the medication to treat their children’s epilepsy, with some parents even moving across the country to states where medicinal marijuana is legal.

But medical experts have been hesitant about using a cannabis derivative called CBD as a treatment for epilepsy without more evidence.

This week, a meta-analysis published in the Journal of Neurology, Neurosurgery and Psychiatry looked for clear evidence that cannabidiol was effective at treating epilepsy, and could help reduce or stop seizures.

Researchers from National Drug and Alcohol Research Centre in Australia, King’s College in London, and other institutions reviewed data from 36 published studies on cannabidiol (CBD) treatment for epilepsy.

Cannabidiol is one of the approximately 200 compounds found in cannabis, or marijuana. However, this marijuana-derived compound does not result in the user becoming high after usage, unlike tetrahydrocannabinol (THC).

The evidence that CBD works

The research team looked at six randomized control studies and 30 observational studies.

Most of the studies involved children with a mean age of 16 years.

From the available research, the team found evidence that CBD can reduce seizures as well as improve quality of life for some patients with epilepsy.

The researchers concluded that evidence pointed to a dramatic drop in seizure frequency in about half the people who took CBD in the studies.

According to two randomized control trials and 17 observational studies, researchers said CBD was associated with a significant drop in seizures.

They also found about 48 percent of people were able to have a reduction of seizures by 50 percent or more.

Most of the patients in the studies were children with the catastrophic forms of epilepsy Dravet syndrome or Lennox-Gastaut syndrome (LGS). These ailments can cause severe impairment in young children, but are not the most common cause of epileptic seizures.

After looking at 14 observational studies, the researchers also concluded that almost 1 in 10 of the study’s subjects became seizure free.

The most common side effects included drowsiness, diarrhea, vomiting, and fever. These symptoms led some participants to withdraw from the studies.

“In many cases, there was qualitative evidence that cannabinoids reduced seizure frequency in some patients, improved other aspects of the patients’ quality of life, and were generally well tolerated with mild-to-moderate [adverse effects],” the study authors wrote.

The researchers called for more random controlled trials to better understand if there are types of epilepsy that respond better to CBD, what dosage should be given, and to confirm findings that CBD helps reduce seizure rates.

They also said there needs to be more research for adults to see if these early findings hold up.

“Most studies in this review were observational and used self-report data, raising concerns about possible patient selection and self-reporting bias,” the authors said. “This concern especially applies to self-report surveys of parents, most of whom were self-selected and so may only include the most satisfied users of cannabinoids.”

While some countries, including Israel, Germany, and Canada, have legalized the drug for medical treatment, the U.S. Food and Drug Administration (FDA) has yet to approve any CBD treatment.

A British company has submitted a CBD-based epilepsy medication to the FDA for approval.

What we still don’t know about CBD

Dr. Fred Lado, Northwell Health’s regional director of epilepsy in New York, said the study published this week was a “valuable contribution” to epilepsy research.

For “cannabidiol, there is some benefit at least in specific types of epilepsy such as Dravet syndrome and LGS,” Lado told Healthline.

Lado said for other forms of epilepsy, the benefits of CBD remain less clear, but this study has helped show why more random control trials are needed to verify early results.

“By looking at the broader literature of experience outside of those narrow types of epilepsy, what they’re saying is ‘Yes there may be some benefit.’ It’s difficult to be sure because of all the limitations of nonrandomized trials,” Lado said.

He said more research and especially double-blind placebo trials are needed in order to account for the placebo effect.

“In order to really know if you’re really helping, you’ve got to really do very, very rigorous studies,” he explained.

He pointed out that the researchers determined from the studies that “you have to treat 171 people to have one person become seizure free, that’s not in excess of what would have happened with a placebo,” he said.

Lado said that while the studies show some benefit of CBD, it’s likely not a silver bullet to stop epilepsy. He added there can be serious side effects, including sedation and a change in liver enzymes.

The CBD findings, are “very much in line with the seizure medicines that we have. This is not a panacea,” he said. “It’s a tool and in some cases, it may be particularly useful, and it also comes with some risks.”