It probably won’t come as a surprise that smoking a joint now and then will leave you feeling … pretty good, man. But smoking a lot of marijuana over a long time might do just the opposite. Scientists have found that the brains of pot abusers react less strongly to the chemical dopamine, which is responsible for creating feelings of pleasure and reward. Their blunted dopamine responses could leave heavy marijuana users living in a fog—and not the good kind.
After high-profile legalizations in Colorado, Washington, and Uruguay, marijuana is becoming more and more available in many parts of the world. Still, scientific research on the drug has lagged. Pot contains lots of different chemicals, and scientists don’t fully understand how those components interact to produce the unique effects of different strains. Its illicit status in most of the world has also thrown up barriers to research. In the United States, for example, any study involving marijuana requires approval from four different federal agencies, including the Drug Enforcement Administration.
One of the unanswered questions about the drug is what, exactly, it does to our brains, both during the high and afterward. Of particular interest to scientists is marijuana’s effect on dopamine, a main ingredient in the brain’s reward system. Pleasurable activities such as eating, sex, and some drugs all trigger bursts of dopamine, essentially telling the brain, “Hey, that was great—let’s do it again soon.”
Scientists know that drug abuse can wreak havoc on the dopamine system. Cocaine and alcohol abusers, for example, are known to produce far less dopamine in their brains than people who aren’t addicted to those drugs. But past studies had hinted that the same might not be true for those who abuse marijuana.