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  • Translational Psychiatry Research Group

CBD – Just Another Expensive Oil?


An increasing number of countries are legalising cannabis for medicinal use. The availability and use of its products are on the rise. The most abundant chemical in the cannabis plant is THC, the chemical that gives you a high. Second to this is CBD, a chemical that has gained a reputation for itself in recent years. It has been described as a miraculous ‘cure-all’ due to the self-reported benefits it has. This includes a variety of mental health conditions: anxiety, depression and addiction for example. A range of CBD-containing products have emerged in the market over recent years, filling shelves with CBD-infused sweets, beverages and beauty products. But is the hype, spending and interest surrounding CBD justified, or is it just another fad?


Amidst its growing use and emergence as a medical buzzword, it is important to understand the acute and long-term effects of CBD. A recent study led by Dr. Michael Bloomfield and colleagues at UCL’s Translational Psychiatry Research Group and Clinical Psychopharmacology Unit investigated the effects of a one-off dose of CBD on the parts of the brain that recognise rewards (reward processing). Their functional magnetic resonance imaging (fMRI) investigation found that CBD had no effect (Lawn et al., 2020).


Reward processing involves different parts of the brain that help us learn what is rewarding from what is not. These parts of the brain are called the reward system. They influence our decisions to seek rewarding things. For healthy people this might include food, money, or prizes. Though for others, this might be drugs or alcohol. Healthy reward seeking drives learning and is important for accomplishing our goals. But when this goes wrong it is associated with addiction, anxiety, or depression. The reward system could therefore be targeted with drugs hopes of improving loss of pleasure, lack of motivation and drug abuse.


CBD may influence reward processing. Interestingly, it appears to have opposite effects to THC which has been shown to make rewards seem less ‘rewarding’ – CBD is thought to make rewards seem more ‘rewarding’. The reason for this might be due to the effect(s) that these drugs have on the reward system. THC and CBD act on a protein in the body called the endocannabinoid type 1 receptor (CB1), which is found in many reward-related brain regions. CBD may strengthen the brain’s response to reward through the changes that occur when it binds to this receptor. If it is shown to do this, it could potentially be used to prevent or treat addictive behaviours. This might work by making a natural reward such as food more rewarding. This in turn would reduce the drive to seek drugs as rewards. It may also be used clinically to help to restore interest in pleasurable activities in patients who are depressed. These are some of the reasons why there is so much interest around CBD in a clinical setting.


In the study, a type of brain scan called functional magnetic resonance imaging (fMRI) was used. It looked at participant’s brain activity when performing a computer game called the monetary incentive delay (MID) task. The task reliably stimulates reward anticipation and reward feedback – two key components of reward processing. The study recruited 28 healthy participants who each performed the MID task on two separate occasions, one of which they were administered an oral dose of CBD (600 mg), and the other a placebo. How they did on the task and brain activity during it was then compared under the influence of CBD versus placebo.


Although the MID task successfully led to brain activity in the reward system, there was no difference between activity observed under CBD compared to placebo. CBD did not increase brain activity in response to reward processing.


Despite these findings, there are several reasons for further investigation: the long-term use of CBD may produce different effects from what was observed in this short-term study; the study only looked at one dose – different doses of CBD may exert different effects (Zuardi et al., 2017); this study demonstrated that CBD does not affect brain activity underlying reward processing in healthy adults, though it may lead to different effects in patients with psychiatric disorders (Hindocha et al. 2018).


As the field progresses, similar studies need to show the mechanisms by which CBD acts to determine how it can be used. This needs to coincide with evidence-based, accessible and clear information for the general public. This should detail the effectiveness, or perhaps lack thereof, of CBD extracts being sold worldwide.


By Ryan Turner and Tinya Chang


References


Hindocha, C., Freeman, T., Grabski, M., Stroud, J., Crudgington, H., Davies, A., Das, R., Lawn, W., Morgan, C. and Curran, H., 2018. Cannabidiol reverses attentional bias to cigarette cues in a human experimental model of tobacco withdrawal. Addiction, [online] 113(9), pp.1696-1705. Available at: <https://pubmed.ncbi.nlm.nih.gov/29714034/> [Accessed 18 July 2020].


Lawn, W., Hill, J., Hindocha, C., Yim, J., Yamamori, Y., Jones, G., Walker, H., Green, S., Wall, M., Howes, O., Curran, H., Freeman, T. and Bloomfield, M., 2020. The acute effects of cannabidiol on the neural correlates of reward anticipation and feedback in healthy volunteers. Journal of Psychopharmacology, [online] p.026988112094414. Available at: <https://pubmed.ncbi.nlm.nih.gov/32755273/> [Accessed 7 August 2020].


Zuardi, A., Rodrigues, N., Silva, A., Bernardo, S., Hallak, J., Guimarães, F. and Crippa, J., 2017. Inverted U-Shaped Dose-Response Curve of the Anxiolytic Effect of Cannabidiol during Public Speaking in Real Life. Frontiers in Pharmacology, [online] 8. Available at: <https://pubmed.ncbi.nlm.nih.gov/28553229/> [Accessed 14 July 2020].

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