THC, the main psychoactive component in cannabis, impairs visual working memory—the ability to temporarily hold visual information in mind. Two double-blind, randomized crossover experiments with 23 healthy adults each found that oral THC (7.5 or 15 mg) reduced working memory performance, increased self-reported mind wandering, and decreased metacognitive accuracy about ongoing task performance. The authors also showed that short task durations and small sample sizes reduce the likelihood of detecting such drug effects.
THC, the main psychoactive component of cannabis, impairs visual working memory—the ability to temporarily hold information in mind. In two double-blind, randomized crossover experiments, healthy adults performed a visual working memory task after taking oral THC (7.5 or 15 mg) or a placebo. THC reduced working memory performance (effect size d = 0.65), increased self-reported mind wandering, and decreased the accuracy of participants' awareness of their own task performance. The findings suggest that THC disrupts working memory both by increasing mind wandering and by reducing metacognitive monitoring. The study also demonstrated that short task durations and small sample sizes can mask such drug effects.