Epilepsy is a debilitating and troubling condition marked by seizures of varying intensity. Unfortunately, its underlying causes are poorly understood, making it a difficult illness to treat. Some forms are very resistant to drug treatments, and sufferers may try over a dozen different drug treatments to no avail. However, cannabidiol (CBD) is showing very positive results as a treatment for epilepsy, with positive effects on seizure rates even in people with highly drug-resistant forms of epilepsy.
The evidence base testing the effects of cannabidiol (CBD) on epilepsy goes back several decades, but the results of these early tests were inconsistent, and researchers were wary of the small scale of the studies. That said, some studies did report good results. For example, one study published in the journal Pharmacology in 1980 gave 15 individuals either CBD or a placebo and tracked their progress for 4.5 months. Of the eight participants who received CBD, four were almost free of seizures for this time period, three saw a partial improvement, and none reported any negative side-effects. 
Although this is a promising result, 15 participants make for a small study. In fact, these earlier trials only amounted to 48 people being tested . This is far from enough to convince the medical profession to consider CBD as a new widespread treatment.
However, news of these results did reach the press, and some parents began medicating their children with CBD-enriched products. Although CBD appears to be well-tolerated on its own, some parents were giving their children high-CBD cannabis strains. Cannabis contains other compounds which may present potential hazards, particularly in children and young adults whose brains are still developing.
However, there is some suggestion that they were getting results – curious researchers ran a very non-scientific survey of these parents (conducted on Facebook), of which 85% said seizures had reduced in their children, and 14% said seizures had stopped altogether. They also reported few side effects — although increased appetite was commonly reported. 
Given the promising results of the initial studies and the fact that some parents were administering cannabis to their children without medical supervision, there was a clear need for more rigorous research. In response to this need, a study was conducted that represents the largest human trial of CBD to date.
The largest trial yet
The study, published in May 2017 in the New England Journal of Medicine, involved 214 participants aged between two and 18 who suffer from Dravet syndrome, a particularly debilitating form of epilepsy with a high mortality rate and, as yet, no approved treatment. 
This study took place over a 14-week period, making this also the longest trial of CBD yet conducted. Participants were either given a daily oral dose of CBD that gradually built up to 20 mg per kg, or a placebo. Every day, either the patients themselves or their caregivers recorded how many seizures they had, and they also received clinical assessments throughout the time period. The results of this trial were impressive: CBD reduced the frequency of convulsive seizures in people with drug-resistant forms of epilepsy by half, from 12 per month to six per month. People in the placebo group reported about the same frequency of seizures.
The participants in this study did report some side effects, including diarrhea and vomiting, although at a level considered adequate for a prescribed medication. This is in contrast to many previous studies which reported no side effects at all. It may perhaps be due to the younger age of the participants, interaction with other medication they were taking, or the larger dose of CBD that they were given. In this case, the dose was gradually increased to 20 mg per kg, while previous studies have typically given around 3 mg per kg.
So far, so good
The main strengths of this trial were the large number of participants and the long time period it covered. This enabled the researchers to give a fair trial to CBD and make it harder to write off the results as a fluke. What’s particularly impressive is that this trial tested CBD against an illness that is highly resistant to treatment. Still, more studies will be needed in order to convince the medical community, but the results so far will only encourage more funding and interest into the beneficial effects of CBD.
Learn more about CBD and how it helps with other ailments, both common and more serious, in an article we published here.