Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology
October 1, 2020
Kirsten C S Adam, Manoj K Doss, Elisa Pabon et al.
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.
Biological psychiatry. Cognitive neuroscience and neuroimaging
January 1, 2020
Manoj K Doss, Jessica Weafer, David A Gallo et al.
A double-blind, placebo-controlled experiment with 24 healthy infrequent cannabis users tested how THC (15 mg oral) affects context-based memory illusions. Participants memorized object pictures on scenes (e.g., a cat on a beach) after THC or placebo. Two days later sober, they discriminated seen objects from similar lures, with context reinstated or changed. THC impaired memory for perceptual details compared to placebo. Context reinstatement increased both correct recognition and false recognition in both conditions. THC did not interact with context effects overall, but post hoc analyses showed THC magnified the context illusion when objects were semantically congruent with their encoding contexts and abolished it when incongruent. Results suggest THC impairs encoding of specific object information more than item-context associations, potentially sparing or increasing distorting effects of context.
Journal of psychopharmacology (Oxford, England)
September 1, 2019
Elisa Pabon, Harriet de Wit
Two double-blind, within-subjects studies tested whether a mobile phone app could detect cognitive impairment from oral doses of ∆9-tetrahydrocannabinol (0, 7.5, 15 mg). In 24 healthy non-daily cannabis users per study, tasks measuring cognitive speed, reaction time, fine motor ability, working memory, and time perception were completed during four-hour sessions at peak drug effect. ∆9-Tetrahydrocannabinol impaired performance on most standardized computer tasks but not on most brief phone tasks. The phone tasks' brevity likely reduced their sensitivity. The findings confirm impairment at two recreational doses but raise doubts about developing a phone-based field sobriety test for cannabis.