Acute effects of THC vs. CBD on recognition memory
CORE conference: Perspectives in cannabis research and education, 2018
Hélène Devillez, Sophie Yorkwilliams, Kent E. Hutchison, L. Cinnamon Bidwell & Tim Curran
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As medical marijuana use becomes more prevalent, users would likely want to use strains that minimize cognitive side effects, so they can function effectively during school or work. Cannabis produces acute memory impairment during intoxication, although regular users may not show these acute decrements in performance. Marijuana contains different cannabinoids that may have differential effects on memory. Cannabidiol (CBD), a non-psychotomimetic component of marijuana (doesn’t produce a “high”), is thought to have cognitively protective properties and may mitigate some of the harmful effects of ∆9-tetrahydrocannabinol (THC). Recent reviews suggest that CBD has no effect on cognition in healthy individuals, but can improve cognition in various pathological conditions including acute THC intoxication and that CBD may counteract the effects of THC. It has also been suggested that CBD reduces THC-related learning and memory impairments in well-controlled human and animal studies. However, most research to date has used low-strength government-grown cannabis (THC ranging from 3% to 6%) that lacks other key cannabinoids (CBD close to 0%) and has been administered in tightly controlled laboratory environments, all of which maximize internal validity, but compromise external validity. Currently, the THC strength of recreational cannabis in Colorado can exceed 25%, and the strength of CBD comes close to 25% in some strains. In this study, we used a mobile pharmacology and phlebotomy laboratory to naturalistically assess real-world cannabis products. Using the mobile pharmacology and phlebotomy lab allowed us to test participants as well as to draw blood to assess cannabinoid levels immediately before cannabis use, and at precise time points post ingestion. We assessed recognition memory performance in marijuana users after self-administration of one of two marijuana strains (THC only or THC+CBD), before both memory encoding and memory retrieval. 31 participants completed the experiment (16 in the THC only group and 15 in the THC+CBD). Participants studied a list of 20 concrete words followed by a recognition memory test. Participants performed the memory task (encoding and retrieval) before (pretest) and after (posttest) they self-administer their assigned strain. Overall, participant’s accuracy was lower during posttest compared to pretest. Accuracy was also compared between participants who used a THC only strain or a THC+CBD strain. We observed a decrease in accuracy between pre- and posttest for the THC only strain group but this was not the case for the THC+CBD group. These results indicate that THC alone impaired memory more so than THC+CBD.
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