Review of Studies on CBD Safety and Efficacy

Most of these references are meta-studies (i.e. summaries of consolidated results of several separate studies), and are by no means comprehensive, but consistently show safety and efficacy. Not only is CBD is found to be safe; but THC is also safe in low, clinical doses.

Alex F. Manini, MD et al, “Safety and Pharmacokinetics of Oral Cannabidiol when Administered Concomitantly with Intravenous Fentanyl in Humans,” Journal of Addiction Medicine, May/June 2015, vol. 9, Issue 3, p 204-210.

This study showed that cannabidiol (CBD) was safe and well tolerated. In this study, CBD was introduced to test its value as a treatment for opioid addiction. Results were significantly positive, although further tests were recommended.


F. Petzke, et al, “Efficacy, tolerability and safety of cannabinoids for chronic neuropathic pain: A systematic review of randomized controlled studies,” PubMed: US National Library of Medicine, National Institutes of Health (NIH), February 2016.

This review of 13 recently published studies showed that cannabinoids were as safe as the placebo (i.e., as safe as taking “nothing”). Efficacy showed improvement in pain, with results across studies ranging from statistically significant (i.e., some improvement) up to 50% reduction. (Note: different formulations of cannabinoids were used in these various studies. This PubMed abstract includes a link to the original article [in German] which lists 32 footnoted references.)


Mary E. Lynch & Fiona Cambell, “Cannabinoids for treatment of chronic non-cancer pain; a systematic review of randomized trials,” British Journal of Clinical Pharmacology, 2011, p 735-744.

This review of 18 published studies demonstrated no serious adverse effects from the use of cannabinoids. Efficacy results showed a significant analgesic effect of cannabinoids compared to placebos, with another reported benefit of a significant improvement in sleep. (This review offers 57 footnoted references.)


Uwe K. Zetti, et al, “Evidence for the efficacy and effectiveness of THC-CBD oromucosal spray in symptom management of patients with spasticity due to multiple sclerosis,” PubMed Central: US national Library of Medicine, National Institutes of Health (NIH), January 2016.

This review included several studies totaling about 1,600 Multiple Sclerosis patients taking a low-dose THC-CBD oromucosal spray versus a placebo. Few patients experienced side effects, which were typically only a mild dizziness or fatigue. There were no psychopathological or cognitive effects. Studies employed a variety of measurement scales and one or more scales showed that all patients in the cannabinoid treatment groups had significant improvement in spasticity over the placebo group. On the self-assessment scales, 74% of patients in the cannabinoid group reported a 30% or greater improvement in spasticity. (This review lists 104 footnoted references.)


GW Pharmaceuticals – Epidiolex (CBD) Study

An FDA Approved CBD Placebo-Controlled Study

GW Pharmaceuticals, a U.K. based company, is focused on developing cannabinoid-based medicines. It’s most notable product to date is Epidiolex.

About Epidiolex

Epidiolex is a liquid formulation of pure plant-derived CBD, which is now FDA approved to use for selected conditions, primarily pediatric and other epilepsy or seizure disorders. GW has conducted extensive pre-clinical research of CBD in epilepsy since 2007. This research has shown that CBD has significant anti-epileptiform and anticonvulsant activity … and has the ability to treat seizures … with significantly fewer side effects than existing anti-epileptic drugs. To date, GW has received Orphan Drug Designation from the FDA for Epidiolex in the treatment of both Dravet syndrome and Lennox-Gastaut syndrome (both are forms of epilepsy).

CLARIFICATION NOTE 1: GW Pharma does not report any special delivery system for increased bio-availability of the CBD in Epidiolex. The doses are also frequent and quite high. The conclusion is that uptake is fairly typical for straight CBD oil – that is, at the low, standard 4% absorption rate.

CLARIFICATION NOTE 2: Epidiolex is expensive, currently costing as much as $32,500 for one full year of use to prevent or reduce seizures.

Study Results

In their studies, Epidiolex achieved the primary endpoint of a significant reduction in convulsive seizures assessed over the entire treatment period compared with placebo (p=0.01).

The study was conducted over a 14-week period, with 120 patients involved. Dosage of CBD was 20mg/kg/day for 61 of the patients, and a placebo for 59 patients.

The median reduction of seizures among the Epidiolex group was 39%.

“The results of this Epidiolex pivotal trial are important and exciting as they represent the first placebo-controlled evidence to support the safety and efficacy of pharmaceutical cannabidiol in children with Dravet syndrome, one of the most severe and difficult-to-treat types of epilepsy,” said Orrin Devinsky, M.D., of New York University Langone Medical Center’s Comprehensive Epilepsy Center. “These data demonstrate that Epidiolex delivers clinically important reductions in seizure frequency together with an acceptable safety and tolerability profile.”