This paper is an overview of what was understood in 2015 about the role phytocannabinoids play in epilepsy. This is an area of considerable interest because most of the current drugs used for treating epilepsy have severe side effects, do not work for all or even most epilepsies, and are only partially effective in most successful treatments.
Phytocannabinoids are found in the cannabis plant. There are over 100 of them and there are more synthetic versions in development or already being used in clinical settings. The use of cannabis for treating epilepsy goes back thousands of years but so far there is “insufficient information to make any conclusions regarding the anticonvulsant effects of cannabis” in the scientific literature. There is anecdotal evidence that cannabis can in fact make epileptic seizures more severe.
Here is the full scientific article if you wish to download it.
Regardless of the lack of substantial scientific evidence, cannabis or cannabinoids are licensed for use for treating epilepsy in some countries. The rest of the paper studies THC, CBD, and their analogs like CBDV as anticonvulsants, and concludes that there are indeed demonstrated anticonvulsant effects. However, there is not enough data for the drugs to pass the clinical threshold that is required for widespread and safe use.
Anecdotal evidence has pointed to cannabis being an effective anticonvulsant medication for thousands of years. People have used it, knowing only that it worked. Even though some states and countries have licensed cannabis or cannabis extracts like CBD and THC for treating epilepsy, the scientific record is lacking.
In studies, mostly rodent models were used to test the anticonvulsant effects of cannabis and cannabinoids. They are usually representative of human biology and are very useful for exploring the mechanisms of action, but they are not large-scale trials. Some of the forms of epilepsy cannabis is thought to treat are rare, but even so, there is a worrying lack of data.
Preclinical trials suggest a role for the endocannabinoid system (which cannabinoids act upon) in the modulation of seizure “threshold and severity”. THC, CBD, and CBDV are explored in some detail in the paper, giving a thorough overview of what is known about the involvement of the endocannabinoid system in epilepsy and the possible methods by which exogenous cannabinoids could be used to modulate and improve epilepsy symptoms.
The causes of epilepsy are complex, varied, and not well understood. The same is true for the endocannabinoid system’s interactions and role in epilepsy. With the picture only partly complete, it is impossible to reliably confirm the action of cannabinoids for epilepsy, even if the anecdotal evidence is substantial.
Unfortunately, the illegality of cannabis makes it difficult to study. For this reason, trials that do get approval are generally small-scale and therefore of limited use. The mechanisms and theorized roles of cannabinoids have been explored to some extent in animal models but they have not progressed to patient trials. The authors point to one double-blind trial that suggested efficacy with epilepsy, which directs future research. This is not enough, however.
Because of their well-established safety profiles and tolerability, the potential for CBD and CBDV to be explored further and potentially used as widespread antiepileptic medications is substantial. They have demonstrated beneficial effects in laboratories, in animal and human models. The anecdotal evidence is impressive but there need to be more large-scale, representative studies carried out on CBD and CBDV before the mechanisms of action and the appropriate usage can be proven.
In conclusion, there is a lot of anecdotal evidence but not much scientific evidence. It sounds like the authors are convinced of the positive effects of cannabis for epilepsy, but they are waiting for more studies to be carried out before making any recommendations.