A natural compound found in cannabis may help to prevent the frequency seizures, according to a review in the Journal of Neurology Neurosurgery & Psychiatry.
The evidence to date, however, is confined to the treatment of children and teens whose epilepsy does not respond to conventional drugs, and rare and serious forms of the condition, warn the researchers.
Approximately 70 and 80 percent of the newly diagnosed with epilepsy managed to control their condition using conventional drugs, but that still leaves up to a third whose condition does not improve.
Early research indicates that naturally occurring compounds found in cannabinoids may reduce seizures. One of these cannabinoids, appears to show promise for reducing seizures.
Researchers trawled databases for relevant published and unpublished studies looking at the potential impact of cannabinoids as an add-on to usual treatment on epilepsy seizures, and published up to October 2017.
From 91 studies they found six clinical trials (555 patients) and 30 observational studies (2865 patients) that were eligible for inclusion in their review.
All the participants with an average age of 16, had rare forms of epilepsy that did not respond to conventional treatment.
Combined reviews of the clinical trial data revealed that CBD was more effective than a dummy (placebo) drug at cutting seizure frequency by 50 percent or more, and improving quality of life.
CBD was also more effective in reducing seizures altogether, although this was still rare.
Risks of side effects such as dizziness and drowsiness was s24 percent higher--while that of serious side effects was twice as high among those taking cannabidiol.
Data from 17 of the observational studies showed that seizure frequency dropped by at least 50 percent in just under half of the patients and disappeared completely in nearly one in 10 (8.5%) in eight of these studies. Quality of life improved in half of the patients in 12 of the studies.
"Pharmaceutical grade CBD as adjuvant treatment in paediatric onset drug resistant epilepsy may reduce seizure frequency," conclude the researchers. "Existing [randomised controlled trial] evidence is mostly in paediatric samples with rare and severe epilepsy syndromes; [randomised controlled trials] examining other syndromes and cannabinoids are needed."