Marijuana: Cannabis is Pleasurable Because it Changes Brain's Reward Center on Cellular Level

Scientists, behavioral researchers and psychologists have known for years that pot can be addictive. But more research has just been published illustrating just how weed can act on our brains.

A group of neuroscientists has studied how “long-term exposure” to the active compound in marijuana could affect the way brain cells are implicated in addiction. They found that the activity of certain neurons they were studying changed over time.

The research happened in an unlikely place: Brigham Young University, which is affiliated with the Church of Jesus Christ of Latter-day Saints. “In general, we downplay marijuana a bit. But really it’s less of a big deal for adults than for adolescents whose brains aren’t fully developed,” says Jeff Edwards, a neuroscientist at BYU.

Legalize it sign A sign with a cannabis leaf during a march calling for the legalization of marijuana, in Paris on May 14, 2016. KENZO TRIBOUILLARD/AFP/Getty Images

Scientists already knew that weed could activate the reward pathway associated with addiction. This study adds more detail to how brain cells around that pathway might modulate it. But this paper’s findings aren’t directly applicable to human health; the experiments were done on brain cells from adolescent mice, not on human brain cells or in live mice.

The National Institute on Alcohol Abuse and Alcoholism reported that 6.3 percent of American adults could have been diagnosed with pot addiction at some point in their lives. (The proper, technical term is “cannabis use disorder” or “marijuana use disorder.”)

The diagnostic criteria for the condition include physical symptoms, such as experiencing cravings or withdrawal. The criteria also include room to consider how the drug may negatively affect a person’s personal or professional life. Similar criteria exist for addiction to other drugs or things. This particular pot-related diagnosis has been included in the Diagnostic and Statistical Manual of Mental Disorders—a key handbook for psychiatrists and psychologists—since 2013.

Marijuana plant Vegas Marijuana plants in Essence Vegas's 54,000-square-foot marijuana cultivation facility in Las Vegas. On July 1, Nevada joined seven other states allowing recreational marijuana use. Ethan Miller/Getty Images

When a person takes drugs, something happens to a group of cells in the brain that make dopamine. Over time, patterns of activity in these cells can contribute to addiction and dependency.

“We’ve known marijuana can lead to an addiction in some people, and we know that it happens because marijuana stimulates dopamine production and makes you feel good,” says Alan Budney, a psychiatrist and substance abuse specialist at Dartmouth’s Geisel School of Medicine. “In terms of demonstrating that it can be addictive, we’re beyond that already.” 

What exactly happens to these dopamine-producing cells can vary, depending on which drug is taken and which receptor and cells the drug can bind to. THC, the active ingredient in pot, can bind to a receptor on brain cells called CB-1. This receptor can be found in mice and human brains, and mostly in the same brain regions in both species, Edwards said.

Edwards used government-issue marijuana compounds for the research. Other than the obvious concerns about drugs being removed from the lab—a concern with any regulated substance at any university—there was nothing particularly notable about doing the research on the BYU campus, he said. “The institution here knew I was doing the research. They didn’t mind.” 

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