RESIDENT: The effects of the compositional ratio of THC/CBD in cannabis products, and implications in the future of Canadian Cannabis Legislation

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Presenting Author(s): Ian King

Date and time: 24 Mar 2018 from 15:15 to 15:30

Location: Hawthorn C  Floor Map

Presenting Author(s) Names:  Ian King


 Learning Objectives:

  1. To provide a brief background on the endocannabinoid system, as well as cannabis, and its main constituent cannabinoid molecules, THC and CBD
  2. Present and critique a few key current studies which examine the effects of administering THC/CBD in differing compositional ratios on human subjects
  3. Discuss the current recommendations guiding the formation of the Cannabis Act in Canada and discuss potential implications of the currently available evidence.

 Literature References:

 Bhattacharyya, S., Morrison, P. D., Fusar-Poli, P., Martin-Santos, R., Borgwardt, S., Winton-Brown, T., ... & Mehta, M. A. (2010). Opposite effects of Δ-9-tetrahydrocannabinol and cannabidiol on human brain function and psychopathology. Neuropsychopharmacology, 35(3), 764-774.

 Englund, Amir, Paul D. Morrison, Judith Nottage, Dominic Hague, Fergus Kane, Stefania Bonaccorso, James M. Stone et al. "Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment." Journal of Psychopharmacology 27, no. 1 (2013): 19-27

 Hindocha, C., Freeman, T. P., Schafer, G., Gardener, C., Das, R. K., Morgan, C. J. A., & Curran, H. V. (2015). Acute effects of delta-9-tetrahydrocannabinol, cannabidiol and their combination on facial emotion recognition: A randomised, double-blind, placebo-controlled study in cannabis users. European Neuropsychopharmacology, 25(3), 325–334.

 Lawn, W., Freeman, T. P., Pope, R. A., Joye, A., Harvey, L., Hindocha, C., ... & Das, R. K. (2016). Acute and chronic effects of cannabinoids on effort-related decision-making and reward learning: an evaluation of the cannabis ‘amotivational’hypotheses. Psychopharmacology, 233(19-20), 3537-3552

 Morgan, C. J. A., C. Gardener, G. Schafer, S. Swan, C. Demarchi, T. P. Freeman, P. Warrington et al. "Sub-chronic impact of cannabinoids in street cannabis on cognition, psychotic-like symptoms and psychological well-being." Psychological medicine 42, no. 2 (2012): 391-400.

 Morgan, Celia JA, Gráinne Schafer, Tom P. Freeman, and H. Valerie Curran. "Impact of cannabidiol on the acute memory and psychotomimetic effects of smoked cannabis: naturalistic study." The British Journal of Psychiatry 197, no. 4 (2010): 285-290.

Morgan, C. J., Freeman, T. P., Schafer, G. L., & Curran, H. V. (2010). Cannabidiol Attenuates the Appetitive Effects of Δ9-Tetrahydrocannabinol in Humans Smoking Their Chosen Cannabis. Neuropsychopharmacology, 35(9), 1879–1885.


 The Canadian government is currently in the process of developing legislation to legalize, regulate and restrict access to cannabis. With the Cannabis Act set to take effect in July 2018, a major challenge facing government officials is the current lack of comprehensive, high-quality research available to guide policy development. Unarguably, one of the most important areas to be further elucidated is the precise chemical composition of the cannabis products that will soon be legally available to the public. One key area of interest surrounds the effects of the ratio of delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Evolving evidence in this area suggests that the interactions between THC and CBD, and their chemical ratio may become important in defining and regulating the potency of cannabis products. In this literature review, a search was made for studies published within the last ten years, which examined the effects of administering THC/CBD in differing ratios on human subjects. The preliminary evidence suggests that THC and CBD have opposing effects on behavioral, cognitive, and psychological domains. This evidence is supported by THC/CBD demonstrating antagonistic activation of multiple correlative brain regions on fMRI imaging. Evaluating the potency of cannabis products may be more complex than simply looking at the absolute values of THC and/or CBD, but also the relative balance between the two constituents. While in its early stages, this area of research may become critical to evaluating/modifying cannabis legislation in Canada moving forward, specifically in regards to regulating production, educating the public and enforcing public safety.

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