Cannabis study suggests THC impairs working memory through increased mind wandering and diminished performance monitoring
By | Beth Ellwood | www.psypost.org
New research published in Neuropsychopharmacology found evidence that cannabis weakens working memory by increasing off-task thinking and by disrupting one’s ability to accurately monitor task performance.
Tetrahydrocannabinol (THC), the main psychoactive ingredient in cannabis, is commonly believed to disrupt working memory. A research team led by Kirsten C. S. Adam notes that little scientific evidence actually supports this theory. Prompted by a lack of consistency in existing data, the researchers conducted their own controlled study, involving a lengthier working memory task and a greater number of subjects than previous studies.
Two separate experiments were conducted, each involving 24 healthy, non-daily cannabis users with an average age of 23. In Study 1, subjects were separated into two groups and either received a 15 mg dose of THC or a placebo pill. In Study 2, subjects were separated into three groups and either received a 7.5 mg dose of THC, a 15 mg dose of THC, or a placebo pill.
Between 2 and 3.7 hours after ingesting the capsules, subjects in both experiments took part in a working memory task that involved recalling a pattern of colored squares on a grid. The two experiments were double-blind — which meant that neither the researchers nor the participants knew who received the placebo and who received the THC.
Researchers found that, in both experiments, those who received the 15 mg THC doses performed significantly worse on the working memory tests, recalling fewer of the colored squares correctly than those who received the inactive pills. Notably, those who received the smaller dose of 7.5 mg of THC did not differ significantly from the placebo group.