A new study suggests marijuana blunts the brain’s reaction to dopamine, making users less responsive to the chemical responsible for feelings of reward and pleasure.
In the study published Monday in the journal Proceedings of the National Academy of Sciences of the United States (PNAS), the researchers studied the brains of 24 marijuana abusers””that is, people who smoked multiple times a day””and how they reacted to methylphenidate, a stimulant often used to treat ADHD and narcolepsy. Using personality tests and brain imaging, the researchers found the pot users had blunted behavioral, cardiovascular, and brain responses to methylphenidate compared to control participants. Marijuana abusers scored lower on tests of positive emotional activity and higher on negative emotional reactions.