Effects of Adolescent Cannabis and Alcohol Co-Use on Reward, Mood and Cognition
Cannabis and alcohol co-use is prevalent in adolescence but its long-term effects on cognition and reward-related behaviours remain largely unexplored. The aim of this study is to investigate the effects of adolescent alcohol and Δ9-tetrahydracannabinol (THC) vapour co-exposure on cognitive- and reward-related behaviours. Male adolescent Sprague-Dawley rats received vapourized THC (10mg/pad) or vehicle every other day and had continuous voluntary access to alcohol (10% volume/volume) to assess the effects of THC on alcohol consumption. In adulthood, rats underwent behavioural testing. Adolescent rats showed higher alcohol preference in the two-bottle choice test, on days on which they were not exposed to THC vapour. In adulthood, rats treated with alcohol as adolescents exhibited short-term memory deficits and decreased alcohol preference; while rats exposed to THC vapour showed learning impairments. Our results indicate that although adolescent THC acutely affects alcohol drinking, adolescent alcohol and cannabis co-use may not produce long-term additive effects.