The use of cannabis affected mood and subjective experience, alcohol impaired cognition and affected psychomotor performance, and the co-use of cannabis and alcohol was at most, additive, according to study findings published in the journal Progress in Neuropsychopharmacology & Biological Psychiatry.
Alcohol and cannabis are the most widely used psychoactive substances worldwide. In 2 recent surveys, the majority of cannabis users (more than 75%) reported co-use of alcohol and nearly a quarter of drinkers aged 18-29 years (23%) reported co-use of cannabis. Despite widespread co-use, there have been few studies published examining their combined effects.
For this study, recreational users of cannabis and alcohol (N=28) were recruited via social media and print advertisements in Canada. The participants were randomized to receive placebo alcohol and placebo cannabis, intoxicating alcohol (target breath alcohol content of 80 mg/dL) and placebo cannabis, placebo alcohol and active cannabis (12.5% tetrahydrocannabinol ad libitum), or intoxicating alcohol and active cannabis. Participants attended a practice and active treatment session in which they provided breath, oral fluid, and urine samples, completed cognitive tests, subjective mood measures, and a driving simulation and were sent home by taxi 5 hours after alcohol consumption.
The study population comprised of 16 men and 12 women, 17 were White, they were aged mean 22.54 (standard error [SE], 0.48) years, mean body mass index was 24.50 (SE, 0.64) kg/m2, they used cannabis 2.93 (SE, 0.30) days per week, and alcohol 2.08 (SE, 0.27) days per week.
Compared with placebo, tension-anxiety change was greater after cannabis (t, -2.78; P =.010) and alcohol-cannabis (t, -2.79; P =.010) consumption and confusion significantly increased after alcohol (t, -2.61; P =.015) and alcohol-cannabis (t, -3.71; P =.001) consumption.
Significant effects for the Addiction Research Centre Inventory (ARCI) measures for morphine-benzedrine (MBG), lysergic acid diethylamine, pentobarbital-chlorpromazine-alcohol, euphoria, and sedation drug classes were observed after alcohol and/or cannabis consumption. For MBG, the effect of alcohol-cannabis combined was significantly greater than placebo or either substance alone (all P ≤.017). Similar trends were observed for euphoria (all P ≤.011).
The substances were observed to effect immediate total recall. In general, performance was poorer among the alcohol recipients compared with either cannabis (t, -2.93; P =.007) or placebo (t, 3.26; P =.003) conditions.
Similarly, the substances had a significant effect on the Digit Symbol Substitution Test (DSST) trials attempted, trials correct, and reaction time. As with recall, alcohol recipients performed the poorest and individuals who received cannabis alone performed similar to placebo recipients.
The major limitation of this study was selecting a target alcohol intoxication level but allowing for ad libitum cannabis use.
“In summary, we found that cannabis significantly affected mood and subjective experience more than cognitive and psychomotor performance, while alcohol significantly affected cognitive and psychomotor performance more than mood and subjective experience. […] Particularly given expanding legalization of cannabis use worldwide, these findings from a nonclinical sample have implications for multiple domains of health and safety related to simultaneous use of alcohol and cannabis including recommendations for lower-risk simultaneous use (eg, avoiding cognitive tasks associated with school or professional duties, operation of a motor vehicle or other heavy machinery),” the researchers concluded.
Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.
Wickens CM, Wright M, Mann RE, et al. Separate and combined effects of alcohol and cannabis on mood, subjective experience, cognition and psychomotor performance: A randomized trial. Prog Neuropsychopharmacol Biol Psychiatry. 2022;110570. doi:10.1016/j.pnpbp.2022.110570