Research Projects

Investigating the Psychological Effects of THC and the Medical Potential of CBD

Dr. James Stone, Institute of Psychiatry , London
Dr. Paul Morrison, Institute of Psychiatry , London
Amanda Feilding, Beckley Foundation, Oxford

Previous studies at the IoP with involving intravenous tetrahydrocannabinol (THC) and healthy controls have revealed an interesting and frequent effect, where the connection between the individual's thoughts and decision making process, and their actions or speech, is disrupted. Given the growing concern over cannabis's role in inducing psychosis and/or schizophrenia in a susceptible few, understanding this disconnect is clearly of great importance to understanding why cannabis might act as a contributing factor to developing these disorders, as well as helping to clarify their physiological basis (particularly the dopamine and endocannabinoid systems' role in these phenomena).

Certain mental states in which actions cease to be correctly recognised as originating from oneself are accompanied by disruption in the coherence of the EEG trace associated with these thought patterns. We will therefore test the hypothesis that THC causes a similar disruption of EEG coherence, and that the worse the disruption is, the more intense the subjective experience of loss of connection between thoughts and speech. This research will help understand how and why cannabis might contribute to states of psychosis, and also identify the role of the endocannabinoid system in determining these states. Such knowledge is vital in the search for a treatment to alleviate these states, as it identifies the neurotransmitter targets that any treatment should seek to manipulate.

At the same time, we will be contributing to the search for such treatments by investigating the efficacy of another component of cannabis, Cannabidiol (CBD), to relieve some of the distressing effects of THC. CBD has already been shown to have anti-psychotic properties so could be an important addition to the limited range of effective treatments for schizophrenia, one of the most debilitating and distressing diseases that mankind suffers from.

The study will therefore rigorously examine the potential of CBD as an anti-psychotic treatment, and will investigate whether CBD is more effective at treating THC-induced psychosis than current anti-psychotic drugs. If CBD is found to be the most effective treatment, we will then investigate the optimal means of delivering it to clinical patients, and from there quickly progress to phase II clinical studies with psychiatric patients. Given the preliminary data, we are extremely hopeful that CBD will prove to be an effective inhibitor of THC-induced psychosis, and that a vital new treatment will be brought to the aid of patients suffering from this most distressing of mental disorders. This research could also help illuminate why modern strains of cannabis have been associated with an increased risk of developing psychosis as such strains are bred and grown to maximise their THC content with no regard to CBD concentrations. Understanding this could lead to the development of safer strains of cannabis for both medicinal and recreational users alike, which might increase the likelihood of decriminalising cannabis and regulating its use as is the case for other drugs such as tobacco or alcohol.