RT Journal Article SR Electronic T1 Δ9-Tetrahydrocannabinol (THC) impairs visual working memory performance JF bioRxiv FD Cold Spring Harbor Laboratory SP 778068 DO 10.1101/778068 A1 Kirsten C. S. Adam A1 Manoj K. Doss A1 Elisa Pabon A1 Edward K. Vogel A1 Harriet de Wit YR 2019 UL http://biorxiv.org/content/early/2019/09/23/778068.abstract AB With the sharply increasing prevalence of cannabis use and availability, there is an urgent need to identify cognitive impairments related to its use. It is widely believed that cannabis, or its main psychoactive component Δ9-tetrahydrocannabinol (THC), impairs working memory, i.e., the ability to temporarily hold information in mind. However, our review of the literature yielded surprisingly little empirical support for an effect of THC or cannabis on working memory. We thus conducted a study with 3 main goals: (1) quantify the effect of THC on visual working memory in a well-powered sample (2) test the potential role of cognitive effects (mind wandering and metacognition) in disrupting working memory, and (3) demonstrate how insufficient sample size and task duration reduce the likelihood of detecting a drug effect. We conducted two double-blind, counterbalanced experiments in which healthy adults (N=23, 23) performed a sensitive and validated visual working memory task (the “Discrete Whole-Report task”, 90 trials) after administration of THC (7.5 and/or 15 mg oral) or placebo. We also assessed self-reported ‘mind wandering’ (Exp 1) and metacognitive accuracy about ongoing task performance (Exp 2). THC impaired working memory performance (d = .65), increased mind wandering (Exp 1), and decreased metacognitive accuracy about task performance (Exp 2). Thus, our findings indicate that THC does impair visual working memory, and that this impairment may be related to both increased mind-\ wandering and decreased monitoring of task performance. Finally, we used a downsampling procedure to illustrate the effects of task length and sample size on power to detect the acute effect of THC on working memory.