Marijuana Use Affects Decision Making

Marijuana use is on the rise, according to data from the National Institute on Drug Abuse. Perceptions that marijuana is a harmless drug are also on the rise, despite increasing evidence that shows an association between marijuana and dangerous side effects such as psychosis. A recent study conducted at Wake Forest Baptist Medical Center provides evidence that chronic use of the drug has a significant effect on how the brain works through the decision-making process. Supported by grants from NIDA, the results of the study were presented at the annual meeting of the College on Problems of Drug Dependence. Lead author Michael J. Wesley, Ph.D. of the department of Physiology and Pharmacology at Wake Forest Baptist explained that the results may help explain continued marijuana use and help in developing strategies for treatment therapy. It is very important, said Wesley, that there be a full understanding of the long-term effects of heavy marijuana use. The results were published in the January 2011 issue of the journal Psychiatry Research. The study used the Iowa Gambling Task (IGT) to measure the decision-making tasks of marijuana users. In the IGT, participants make choices within ambiguous circumstances and win or lose money based on those choices. The IGT uses the data of the participants’ choices to guide future maneuvering toward safe choices that result in more wins and fewer losses. The researchers compared 16 chronic marijuana users to 16 controls and performed the IGT in an MRI scanner. The performance of the participants was tracked and the researchers examined the brain activity as the participants experienced early wins and losses. The researchers were examining whether poor performance in marijuana users was related to exhibited brain activity while the participants were evaluating their decisions. While the members of the control group were effectively guided to safer answers, those in the marijuana users group generally failed to follow the pattern guided by the system to safer answers, but instead continued to choose risky options. The observations conducted by the researchers showed that this was because the marijuana users were less sensitive to the negative feedback during early stages of the task. The marijuana users seemed to have a blunted response to losing in the task, explained Wesley. The participants are unable to develop a strategy for avoiding monetary losses, which exhibits a decreased function in brain response to the early information provided in the system’s responses that helps the participant choose safer options. The results of the study highlight the importance of education and prevention programs that help deter drug use. The information provided in the study about the negative effects on decision-making when marijuana is used may help discourage use.

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