Todd Subritzky, PhD

What is Delta 9 Tetrahydrocannabinol?

Now we are really getting into the technical aspects of medical cannabis related pharmacology. THC or Tetrahydrocannabinol was first identified by Gaoni and Mechoulam (1964). It is known as one of the most prominent cannabinoids in most cannabis strains and is the primary psychoactive ingredient in the plant. In other words, THC is the cannabinoid responsible intoxication when cannabis is consumed.

There are currently two THC chemical classes that have been identified in the plants, namely Delta 8 Tetrahydrocannabinol and Delta 9 Tetrahydrocannabinol. According to ElSohly and Waseem (2014), these two classes each consist of multiple compounds with Delta 9 THC including 18 separate compounds, while Delta 8 THC has just two. While both THC classes induce intoxication, “because Delta-9-THC is much more abundant than Delta-8-THC, the psychoactivity of marijuana has been attributed largely to the effects of Delta-9-THC” (Institute of Medicine, 1999).

Recent studies indicate that the behavioral effects of THC are receptor-mediated. More specifically, neurons in the brain are activated when a compound binds to its receptor. Binding to a receptor results in a change in the cell’s activity, the regulation of its genes, or the signals that it sends to neighboring cells. Delta 9 THC most commonly binds with the CB1 and CB2 receptors, which are a core function of the human endocannabinoid system.

CB1 and CB2 cannabinoid receptors of the endocannabinoid system

“CB1 is the psychoactive, neuro-modulatory, and analgesic receptor” (Russo, 2016, p.2). It is to be found in relatively low concentrations in some ‘peripheral non-neuronal tissues’ such as liver, heart, stomach, fat tissue, and testis, although its main localization is in the nervous system (Szabo, 2014).

CB2 has been described as “an anti-inflammatory immunomodulatory receptor” (Russo, 2016, p.2). Initially, it was thought that the CB2 receptor was limited to peripheral immune-related organs including the spleen, thymus, and tonsils, however current observations indicate CB2 receptors are also present in neurons – yep, the brain. For example, CB2 receptor mRNA or protein has been located in regions such as the hippocampus, cerebral cortex, and spinal sensory neurons (Szabo, 2014). In comparison to CB1 receptors, CB2 receptors have more restricted distribution and much lower density.

Medical potential for Delta 9 THC

Research continues into the therapeutic potential of THC with new research quickly evolving. According to Carlini (2004), “Under the clinical point of view, Delta(9)-THC produces some therapeutic benefits which are beyond a reasonable doubt. Thus, the effects on nausea/emesis due to cancer chemotherapy, as appetite promoter, on some painful conditions and on symptoms of multiple sclerosis are clearly demonstrated”. Other areas of potential therapeutic value for Delta 9 THC include heart disease (Blesching, 2015). Indeed, Delta 9 THC is almost certainly the most studied constituent in cannabis, nonetheless “this unique molecule keeps surprising scientists as new information comes to light about its immense influence on human physiology and psychology” (Blesching, 2015).



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ElSohly, M., & Waseem, G. (2014). Constituents of cannabis sativa. In R. Pertwee (Ed.), Handbook of Cannabis. New York, NY: Oxford University Press.
Gaoni, Y., & Mechoulam, R. (1964). Isolation, structure, and partial synthesis of an active constituent of hashish. Journal of the American chemical society, 86(8), 1646-1647.
Institute of Medicine. (1999). Marijuana and Medicine: Assessing the science base. Washington, D.C.: National Academy Press.
Russo, E. (2016). Beyond Cannabis: Plants and the Endocannabinoid System. Trends in Pharmacological Sciences, 37(7), 594-605. doi:
Szabo, B. (2014). Effects of phytocannabinoids on neurotransmission in the central and peripheral nervous systems. In R. Pertwee (Ed.), Handbook of Cannabis. New York, NY: Oxford University Press.