Identifying The Neurobiological Correlates Of The Subjective Effects Of Cannabis That Users Find Beneficial


in Cannabis,Research

Prof. David Nutt, University of Bristol
Dr. Robin Tyack, University of Bristol
Dr. Andrea Malizia, University of Bristol

Amanda Feilding, Beckley Foundation, Oxford

‘Ultimately, there may be advantages to acknowledging the benefits of drug use. One would be to indicate reasons why people are self-medicating and find safer agents to meet these needs. A better demarcation between harder and softer drugs might feasibly reduce progression to harder drugs…. Testing benefits might also render drug policy more credible, with reduced demonisation of drug users and hypocrisy, which might overall improve drug prevention efforts.’ Robert MacCoun, Professor of Law and Public Policy at the University of California, Berkeley, USA.

Despite decades of research into the effects of cannabis, no studies have investigated the subjective benefits or examined the neural and physiological correlates underlying the experience that cannabis users find beneficial. Cannabis is the most commonly used illicit drug worldwide and the pattern of usage has been steadily increasing over the past 40 years. The long-term health effects of cannabis are poorly understood, but there is increasing concern about the suggested link between modern cannabis use and psychosis or the induction of anxiety symptoms. Such concerns however stand in stark contrast to the subjective reports of many users who find cannabis positive and anxiety relieving.

Cannabis is by far the most-used illegal drug in the world, currently estimated by the UN to be used by 195 million people (4.4% of the world population – as opposed to just 1% of the world population using other illegal drugs). For this reason research is essential to investigate not only cannabis’s potential harms, but also its potential benefits, helping to explain why so many people choose to use it. This project is the first research to investigate the neurophysiological changes underlying the experience of the ‘high’ that users find beneficial when smoking cannabis

This study will therefore document as closely as possible the detailed changes that occur within the brain during acute cannabis intoxication, and relate these physiological effects to the subjective experiences associated with cannabis consumption. It will use multiple neuroimaging modalities to monitor cannabis-induced changes in blood flow and neurotransmitter concentrations, and so fill vital gaps in our knowledge base of exactly how cannabis affects brain functioning. Vaporised cannabis will be used as the test substance, an important innovation compared to previous studies which have relied upon the administration of pure tetrahydrocannabinol (THC), the main, but not only, psychoactive compound in cannabis, as a proxy for cannabis consumption. This study should therefore give a much better scientific understanding of cannabis’ actual effects.

David Nutt

Recent publicity has linked long-term cannabis use, particularly among the young with the possibility of triggering anxiety or psychosis in a vulnerable minority with a genetic predisposition. This is in stark contrast to subjective reports of the majority of people who find quite the opposite – that cannabis is a recreational and/or therapeutic drug that can alleviate the symptoms of a great variety of illnesses, and can also elevate mood, overcome stress, and stimulate creativity or social interaction. Our study will also investigate why cannabis causes such different reactions in different people, being anxiolytic to some and anxiogenic to others.

Key to this inconsistency is the fact that little research into cannabis has been carried out since the 1970s, and that most such research has used intravenously-administered tetrahydorcannabinoid (THC), the psychoactive compound in cannabis. However, cannabis has over 400 chemical components, making intravenously-administered THC alone an unsatisfactory model of ‘street’ cannabis use. This is one of the first studies to use the natural plant with all chemical components, administered using a vaporiser.

This study fits into many of the Beckley Foundation’s research objectives, by increasing our understanding of why people use cannabis and of the physiology underlying its various effects, throwing light on the changes in cerebral circulation, neurotransmitter activity, brain activity and emotional response, correlated to subjective experience.

Whilst most research has focussed on the basic physiological effects of cannabis, this study will teach us much more about why people use cannabis. Furthermore, its simultaneous use of multiple neuroimaging technologies enables a detailed understanding of the complex interaction between neurotransmitter systems and blood flow in specific parts of the brain. It will enable us to correlate these quantitative indicators of brain physiology and chemistry with the data on qualitative changes in cognition and subjective experience. This will improve our understanding of the physiological basis for a range of conscious states, from the positive states of high awareness to the anxiety that users can sometimes experience.

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