Cannabidiol (CBD) could be a safe and effective treatment for problematic cannabis use, according to new findings from a benchmark clinical trial involving UCL.
The study, published today in The Lancet Psychiatry, was the first-ever randomised clinical trial of CBD, a non-intoxicating constituent part of the cannabis plant, for cannabis use disorder.
For the Medical Research Council-funded trial, the researchers administered CBD or placebo to 82 volunteers who were motivated to quit using cannabis but had previously failed to do so. They measured the effects of the drug on levels of cannabis use both during a four-week treatment period and up to six months follow-up.
They tested three different doses of CBD in an adaptive design to find out which doses might be most effective.
In the first stage of the trial, 48 volunteers received either placebo or CBD at doses of 200mg, 400mg or 800mg. The researchers found that the lowest dose of 200mg CBD was ineffective and so they dropped it from the trial.
In the second stage of the trial, the researchers recruited an additional 34 volunteers to receive either placebo, 400mg or 800mg CBD. At the end of the trial, they found consistent evidence that CBD at 400mg or 800mg was more effective than placebo at reducing cannabis use.
Senior author Professor Valerie Curran (UCL Clinical Psychopharmacology Unit) said: "Our findings indicate that CBD doses ranging from 400mg to 800mg daily have the potential to reduce cannabis use in clinical settings, but higher doses are unlikely to bring any additional benefit. Larger studies are needed to determine the magnitude of the benefits of daily CBD for reducing cannabis use."
The results showed that participants treated with CBD showed lower levels of cannabis in their urine and an increased number of days abstinent compared to those treated with placebo.
CBD was well tolerated at all doses and there were no increases in side effects compared to placebo. 94% of the volunteers completed treatment. Importantly, the doses of CBD tested were significantly higher than CBD products purchased online or from the high street (typically 25mg per day).
All participants in the trial met a clinical diagnosis of cannabis use disorder, indicating a problematic pattern of cannabis use which had created significant impairment and distress for the individual. All participants had previously failed to quit cannabis use at least once and took part in the trial as part of a cessation attempt.
Lead author Dr Tom Freeman (University of Bath and honorary researcher, UCL Psychopharmacology Unit) explains: "The results from our trial open up a novel therapeutic strategy for managing problematic cannabis use in clinical settings. As we highlight, CBD at daily oral doses of 400mg and 800mg has potential to address the substantial and currently unmet clinical need for a pharmacological treatment of cannabis use disorders."
"Whilst it may seem counterintuitive to treat problematic cannabis use with CBD - a constituent part of the cannabis plant - THC and CBD have contrasting effects on our own endogenous cannabinoid system. Unlike THC, CBD does not produce intoxicating or rewarding effects and it shows potential for a treating several other medical disorders."
Cannabis is now the primary drug cited by first-time clients presenting at addiction services across Europe, with the number of people entering treatment increasing by 76% over the past decade. The increase in treatment for cannabis problems has occurred alongside an increase in concentrations of THC, the intoxicating component of cannabis. Daily use of cannabis with high THC concentrations is associated with a five-times increased risk of psychosis.
At present there are no recommended pharmacotherapies to help people with problematic cannabis use to quit. In demonstrating how CBD could be a promising treatment strategy, this trial adds to existing research on the potential medicinal uses of CBD including the treatment of severe childhood epilepsy syndromes and psychosis. Importantly, treatment with CBD does not include any of the intoxicating constituent of cannabis (THC) which might carry a risk of adverse effects.