Heavy Cannabis Use Compromises Brain's Dopamine System

Marijuana, despite what many will claim, is not a benign substance and carries the risk of addiction. All over the country, more and more people are in favor of doing away with marijuana prohibition, in favor of both medical and recreational marijuana legislation. This fall, a number of states are expected to vote on legalizing the controversial drug. Whether legalization is a good or bad thing is up for debate; however, the change in stance on marijuana has allowed for research that was previously impossible to conduct.

In recent years, a number of studies have been conducted dealing with cannabis use and the drug's effect on the brain. If we are going to vote on the legality of a drug, it is crucial we have all the facts. It turns out, that marijuana’s impact on the brain may not be too dissimilar to other, more dangerous drugs. New research suggests that heavy cannabis use compromises the brain's dopamine system, Science Daily reports. Heavy cannabis use can impact the striatum - the region of the brain responsible for working memory, impulsive behavior, and attention. The findings were published in the journal Molecular Psychiatry.

"In light of the more widespread acceptance and use of marijuana, especially by young people, we believe it is important to look more closely at the potentially addictive effects of cannabis on key regions of the brain," said lead author Anissa Abi-Dargham, MD, professor of psychiatry (in radiology) at Columbia University Medical Center (CUMC). 

The researchers used positron emission tomography (PET) on 11 adults severely dependent on cannabis and 12 matched healthy controls, according to the article. The heavy cannabis users had significantly lower dopamine release in the striatum, compared to the controls. Lower dopamine release was associated with worse performance on learning and working memory tasks.

"We don't know whether decreased dopamine was a preexisting condition or the result of heavy cannabis use," said Dr. Abi-Dargham. "But the bottom line is that long-term, heavy cannabis use may impair the dopaminergic system, which could have a variety of negative effects on learning and behavior."