Effects of daily Δ
Daily use of marijuana is rising in adolescents, along with consumption of high potency marijuana products (high % Δ-9-tetrahydrocannabinol or THC). These dual, related trends have opened gaps in understanding the long-term effects of daily consumption of a high dose of THC in adolescents and whether a therapeutic dose of cannabidiol (CBD) modulates THC effects. Adolescent squirrel monkeys (Saimiri boliviensis) were treated daily for four months with vehicle (n 4), a high THC dose (1 mgkg i.m. n 4), or THC CBD (1 mgkg 3 mgkg i.m. n 4), to investigate whether (1) a daily high THC dose affects performance in tasks of cognition (repeated acquisition, discrimination reversal) (2) a daily high THC dose affects spontaneous behavior and daynight activity (3) tolerance develops to the behavioral effects of THC (4) whether CBD modulates THC effects. THC impaired performance of adolescent monkeys in a cognitive test initially, but not performance on a task of cognitive flexibility. THC reduced motor activity and increased sedentary behavior, with tolerance developing after weeks of daily treatment. Co-administered with THC, CBD did not modulate THC effects on cognitive performance, activity or tolerance, but prevented THC-induced emesis on the first day of daily treatment. Daily high dosing with THC compromised performance on a task of cognition, and reduced activity in adolescent primates, with tolerance developing within weeks. Whether our observations are relevant to a broader range of cognitive tasks vital for daily function in human adolescents is uncertain.