A single large dose of cannabidiol (CBD) does not alter brain activity in several reward-related brain regions, according to a new double-blind, placebo-controlled study. The findings appear in the Journal of Psychopharmacology.
“The last few years have seen a surge in interest in CBD as a wellness supplement and a potential psychiatric medicine. CBD’s effects on the human reward system may underlie some of these putatively positive impacts,” said study author Will Lawn, a post-doctoral research associate at the Clinical Psychopharmacology Unit at University College London.
In the study, 23 healthy participants received 600 mg of CBD during one experimental session and a placebo during another session. The order of the CBD/placebo conditions was randomized for each participant.
After receiving their dose, the participants completed a brain-scanning test called the Monetary Incentive Delay Task, or MID, which is used to examine the neural correlates of reward anticipation and reward feedback.
The computerized test requires participants to push a button as quickly as they can whenever they see a white square on the screen. Pressing the button fast enough sometimes results in winning a small sum of money. During the test, the researchers used functional magnetic resonance imaging (fMRI) to record the brain activity of the participants.
Lawn and his colleagues found that the task was associated with heightened brain activity in several reward-related brain regions, including in the insula, caudate, nucleus accumbens, anterior cingulate and orbitofrontal cortex. But they found no difference between the CBD and placebo conditions.
“In healthy volunteers with no mental health disorders, a single large oral dose of CBD did not alter functional brain activity in the human reward circuit,” Lawn told PsyPost.
The results are surprising because CBD has previously been found to alter reward-related behaviors, and a study in 2020 even found evidence it could reduce cannabis consumption. “The present results leave open the intriguing possibility that CBD may only exert an effect on reward networks that have already been perturbed,” the researchers said.
The authors of the study believe more research is needed. The current study only examined the effects of CBD after a single dose. Habitual consumption of the substance could have other effects.
“Long-term, daily administration of CBD may have very different consequences to a single dose of the drug. Furthermore, the effects of CBD in people who have psychological disorders like depression and addiction should be examined,” Lawn explained.
“The dose of CBD used here (600mg), and those used in clinical trials, are orders of magnitude greater than the almost homeopathic doses (e.g. 1-5mg) of CBD which people get from a few drops of over-the-counter CBD oil bought from health-food stores. Therefore, it is unlikely that these much smaller quantities of CBD alter the reward circuitry in the brains of paying customers.”
“Having said that, the effects and safety of these over-the-counter low-doses have not been formally investigated,” Lawn said. “Research should be conducted into the potentially beneficial, or entirely non-existent, effects of low-dose CBD administration across a range of psychological and physical domains. There is lots more work to be done.”
The study, “The acute effects of cannabidiol on the neural correlates of reward anticipation and feedback in healthy volunteers“, was authored by Will Lawn, James Hill, Chandni Hindocha, Jocelyn Yim, Yumeya Yamamori, Gus Jones, Hannah Walke, Sebastian F. Green, Matthew B. Wall, Oliver D. Howes, H. Valerie Curran, Tom P. Freeman and Michael A. P. Bloomfield.