Collaboration with Dr Paul Morrison

This research investigated the effects of cannabidiol (CBD) and its relationship to THC (the psychoactive ingredient in cannabis), and how this might affect psychotic symptoms, using brain imaging and EEG. The studies were among the first to explore CBD’s anxiety-lowering and anti-psychotic properties, and they paved the way to evaluating the therapeutic potential of endocannabinoids such as CBD.

This series of studies evaluated the effects of THC and CBD on the brain, as well as on cognitive function and symptoms related to psychosis. Research with fMRI showed that THC and CBD produced opposite effects on regional brain function during task performance. CBD also showed the potential to block certain negative effects of THC, highlighting its therapeutic properties: individuals treated with CBD before being under the influence of THC were less likely to exhibit psychotic symptoms and to experience memory impairment.

The research also dismissed the long-standing hypothesis that cannabis-elicited psychosis was related to the release of dopamine. While THC seemed to catalyse psychotic-like effects in some individuals, this did not correspond to a significant increase in dopamine release.

Additional studies measured ‘brain waves’ (synchronised oscillations in neuron firing patterns), and found a correlation between THC-elicited psychosis and changes in ‘brain waves,’ specifically a reduction in theta-band coherence in left and right frontal cortex. This suggests that the pro-psychotic effects of THC might be related to impaired communication between the right and left frontal lobes. Moreover, THC disrupted the synchronisation of ‘brain waves’ preceding speech. This is also the case in patients with schizophrenia, which could explain the acute psychotic-like effects experienced by some cannabis users.

Finally, the research assessed the effects of THC on self-timed actions and self-rated perceptions of time distortion, and showed that two different brain mechanisms might be responsible: the former might be influenced by impaired concentration, while the latter might relate to higher brain function.

Research Team and Institution

Kings College London is one of the world’s leading Universities for both education and research. King’s has become the largest centre for graduate and post-graduate medical teaching and biomedical research in Europe as per number of students and is regarded as one of the leading multidisciplinary research universities in the world. The Institute of Psychiatry, Psychology and Neuroscience is a research institution at King’s College, dedicated to discovering what causes mental illness and diseases of the brain, and identifying prevention and treatment avenues.

Paul Morrison is a psychiatrist and researcher at The Institute of Psychiatry. He has completed a number of experimental studies focused on the issue of cannabis and psychosis. At present he works to advance trials of promising new treatments for major mental illness, specifically focusing on trials of CBD for psychosis.