Δ9-Tetrahydrocannabinol (THC) impairs visual working memory performance: a randomized crossover trial.
Kirsten C. S. Adam, Manoj K. Doss, Elisa Pabon, Edward K. Vogel, Harriet de Wit
Neuropsychopharmacology October 1, 2020 DOI: 10.1038/s41386-020-0690-3 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Randomized controlled trial Double-blind Peer reviewed |
|---|---|
| Sample size | 23 |
| Population | Healthy adults |
| Intervention | THC |
| Dose | 7.5 and/or 15 mg oral |
| Topics | Cannabis |
| Citations | 2 |
| Key findings | THC impaired visual working memory performance (d = 0.65), increased mind wandering, and decreased metacognitive accuracy about task performance. |
Abstract
With the increasing prevalence of legal 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 three 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, randomized crossover experiments in which healthy adults (N = 23, 23) performed a reliable 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 = 0.65), 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 down-sampling procedure to illustrate the effects of task length and sample size on power to detect the acute effect of THC on working memory.
Comparable studies
Other randomized controlled trials on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment Healthy participants | 2012 | Randomized controlled trial | n = 48 |
| Distinct Effects of Δ9-Tetrahydrocannabinol and Cannabidiol on Neural Activation During Emotional Processing Healthy, English-native, right-handed men who had used cannabis 15 times or less in... | 2009 | Double-blind, randomized, placebo-controlled crossover trial | n = 15 |
| Acute Effects of a Single, Oral dose of d9-tetrahydrocannabinol (THC) and Cannabidiol (CBD) Administration in Healthy Volunteers Healthy male subjects | 2012 | Randomized controlled trial | n = 16 |
| Modulation of Mediotemporal and Ventrostriatal Function in Humans by Δ9-Tetrahydrocannabinol Healthy, native English-speaking, right-handed men of white race/ethnicity who had used... | 2009 | Randomized controlled trial | n = 15 |
| Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognition Healthy volunteers with a history of light cannabis use | 2019 | Randomized, double-blind, within-subjects crossover | n = 14 |
Citations in the library
Cited by 17
- Cannabis increases susceptibility to false memory Proceedings of the National Academy of Sciences February 10, 2020
- The acute effects of psychoactive drugs on emotional episodic memory encoding, consolidation, and retrieval: A comprehensive review. Neuroscience & Biobehavioral Reviews July 1, 2023
- The altered state of consciousness induced by Δ9-THC. Consciousness and Cognition May 28, 2022
- Vaporized Δ9-tetrahydrocannabinol exposure in utero has negative effects on attention in a dose- and sex-dependent manner. Pharmacology, Biochemistry, and Behavior September 1, 2024
- Ayahuasca enhances the formation of hippocampal-dependent episodic memory without impacting false memory susceptibility in experienced ayahuasca users: An observational study. Journal of Psychopharmacology April 1, 2025
and 12 more in the library
Cites 14
- Lost in the Sauce Psychological Science April 28, 2009
- Dissociable effects of cannabis with and without cannabidiol on the human brain’s resting-state functional connectivity Journal of Psychopharmacology April 23, 2019
- Δ9-Tetrahydrocannabinol During Encoding Impairs Perceptual Details yet Spares Context Effects on Episodic Memory. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging 2020
- Developing a phone-based measure of impairment after acute oral ∆9-tetrahydrocannabinol. Journal of Psychopharmacology September 1, 2019
- Acute and Chronic Effects of Cannabinoids on Human Cognition-A Systematic Review. Biological Psychiatry April 1, 2016
and 9 more in the library