Research from University College London (UCL) reveals that one large dose of CBD does not change brain activity in a number of regions of the brain associated with reward.
Over two sessions, a research team from UCL administered a single 600mg oral dose of cannabidiol and a placebo to twenty-three healthy participants.
The double-blind, placebo-controlled study, published in the Journal of Psychopharmacology, aimed to test the researchers’ hypothesis that brain activity would be higher after consuming the CBD dose than after the placebo.
Speaking to PysPost, study author Will Lawn, a post-doctoral research associate at the Clinical Psychopharmacology Unit at University College London, said: “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.”
Once the participants received their dose, they underwent a brain-scanning test known as the monetary incentive delay task (MID). A popular technique used by scientists to assess neural responses to the anticipation and delivery of rewarding stimuli.
The test involved participants pushing a button as quickly as they could; if they reacted fast enough, they had a chance of receiving a small monetary reward.
As expected, the task prompted heightened brain activity during anticipation for and the reception of a reward. This was particularly apparent in several reward-related areas of the brain such as the insula, caudate, nucleus accumbens, anterior cingulate and orbitofrontal cortex.
However, across the whole brain, the researchers reported no evidence that CBD altered reward-related activity compared to the placebo.
The authors of the paper said: “Our Bayesian analyses showed that activity in our regions-of-interest was similar following cannabidiol and placebo. Additionally, our behavioural measures of motivation for reward did not show a significant difference between cannabidiol and placebo.”
The findings from the paper conflict with previous research which has shown that CBD could have an effect on reward networks, including a 2020 study which concluded that CBD could be a potential treatment for cannabis use disorder.
According to the researchers, however, this was the first study of its kind to examine the effects of CBD alone on reward-related brain activity.
The authors said: “Previous studies have often investigated how inhaled CBD moderates THC’s effects which may have contributed to the discrepancy. Moreover, other studies have explored more complex components of reward function, including attentional bias toward drug pictures.”
As with most areas of cannabis research, more work is needed. The paper concludes that although CBD did not “acutely affect” the neural links of reward anticipation and feedback, future research is required.
The researchers suggest that further studies should explore the effects of CBD on different components of reward processing and different doses and administration methods should be used.
As this particular study looks at healthy participants, they also advise that people with psychiatric disorders should be assessed as the reward system is believed to play a critical role in a number of psychiatric disorders, including depression.
“Future neuroimaging research should therefore administer CBD to participants thought to have perturbed reward systems, including those with addiction,” the researchers said.
One possible avenue of research that the authors suggest is the binding of CBD to the serotonin-1a receptor as a possible method for disrupting the symptoms of addiction and depression.
“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 told PsyPost.