Dissertation Defence: The Effects of Acute Ingested Cannabis Intoxication on Reaction Time and Reaching Tasks

Quinn Malone, supervised by Drs. Brian Dalton and Chris McNeil, will defend their dissertation titled “The Effects of Acute Ingested Cannabis Intoxication on Reaction Time and Reaching Tasks” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Kinesiology.

An abstract for Quinn Malone’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. Registration is not required for in-person exams.

Abstract

Our knowledge of the impacts of acute cannabis intoxication on motor behaviour is limited. Considering ~25% of Canadians consumed cannabis in 2024, improving our understanding of how the two most highly concentrated cannabinoids commonly found within cannabis products, Δ9-tetrahydrocannabinol (THC; the psychoactive component) and cannabidiol (CBD), is imperative. This dissertation examines several motor activities which represent common components of many activities of daily living to determine how they are impacted and to make inferences concerning the activity of THC and CBD in the central nervous system. Fifteen infrequent cannabis users (≥1/week) performed five types of reaction time (simple, go/no-go, 2-, 4-, and 8-choice) and four types of reaching (a six-target linear vertical reaching with and without electrical vestibular stimulation, and a five-target vertical discrete Fitts’ Task with and without target outlines) tasks. Each participant attended four sessions. During each session they received one of four gel capsule interventions in a counterbalanced order: 10mg THC, 10mg CBD, 10mg THC + 10mg CBD, and a placebo (Vitamin E). Each session consisted of a ~2.5h pre-intervention data collection block, a 2h break to allow for onset of subjective effects of intoxication, and a 2h post-intervention data collection block. Compared to the placebo, both interventions containing THC resulted in slower reaction times and reaching as well as less accurate movements, while the CBD intervention caused slower but more accurate reaching movements. Consuming both THC and CBD caused greater motor deficits than consuming THC alone while reaching. Additionally, the THC intervention was also found to alter sensorimotor processes which integrate vestibular feedback into postural adjustments while performing a reach. These results demonstrate that consuming THC leads to detrimental effects on human [DB1.1]movements, that CBD also impacts motor behaviour, and that the combination of THC and CBD leads to greater movement deficits than THC alone. The outcomes provide information to cannabis users concerning how their movement changes while high, generated hypotheses concerning the mechanisms of action of THC and CBD within the central nervous system[DB2.1][QM2.2], and offer avenues for further research into the impacts of cannabis intoxication on human motor behaviour.