Chronic Δ-tetrahydrocannabinol exposure during adolescence is associated with persistent behavioural tolerance in adult nonhuman primates.

Background And Purpose: Legalisation of Cannabis use has led to considerable increases in the availability and potency of Cannabis products, as well as evolving patterns in methods of their consumption. Adolescent Cannabis use has increased, which can impair cognitive function during this critical developmental stage. The persistence of such effects into adulthood, however, is unclear. The present study examined whether chronic Δ-tetrahydrocannabinol (Δ-THC) exposure during adolescence modifies subsequent Δ-THC-induced cognitive deficits during adulthood.

Experimental Approach: Female and male adolescent nonhuman primates were treated intramuscular daily for 6 months with either vehicle, a low dose of Δ-THC (0.32 mg kg day), or a high dose (3.2 mg kg day). Approximately 1 year after discontinuing chronic exposure, these subjects, now adults, were trained on a touchscreen-based Psychomotor Vigilance Task (PVT) to examine attentional processes. Acute doses of Δ-THC were administered prior to select test sessions via two routes, intramuscular or oral, to evaluate the roles of adolescent drug history and method of consumption on Δ-THC-induced attentional deficits.

Key Results: Results confirm dose-related Δ-THC impairment of PVT performance by both intramuscular and oral routes of administration, notwithstanding differences in potency and onset of action. Adolescent drug history modified tolerance to Δ-THC impact on attentional processes, where subjects exposed to chronic Δ-THC during adolescence required higher doses of Δ-THC during adulthood to impair PVT performance.

Conclusions And Implications: These findings suggest a persistent impact of adolescent Δ-THC use that, even following extended abstinence, may present itself during adulthood via increased tolerance to Cannabis products.