Addiction in the DNA? Three genes linked to heavy pot smoking

Researchers studied about 15,000 marijuana addicts to discover the common threads in their DNA.

SAN ANTONIO - Researchers have discovered a biological link between heavy pot smokers, paving the way for prevention opportunities.

A study, published this month in JAMA Psychiatry, reveals three genes linked to marijuana addiction. Authors James T. R. Walters and Michael J. Owen noted the growing concern: "Cannabis is the most widely used illicit drug in the world, and debate about the impact of its use has been fueled by policies of decriminalization and legalization."

John Roache, psychiatry professor and chief of the Division of Alcohol and Drug Addiction at UT Health Science Center San Antonio, said "this is a first finding for marijuana."

"Most people aren't. A few people are marijuana addicted, and they were more likely to have these genes," he said.

John Allen, a 44-year-old San Antonian, smoked pot for three decades.

"As I got into high school, started using it pretty much every day from when I woke up to pretty much when I went to bed," he said.

Until recently, Allen would have been considered dependent on marijuana. Fewer than 10 percent of pot smokers fall into that category, according to Roache.

"You could say it caused some problems, killed some ambitions, made me a little on the lazy side," said Allen, who's now three months clean, thanks, in part, to the Recovery Center in downtown San Antonio.

Researchers studied about 15,000 people like Allen to discover the common threads in their DNA.


"Are they going to become an addict if they have that gene? No, but they have an increased risk of becoming an addict," Roache said.

The professor added the study could pave the way for a biological test - a blood or hair follicle test, for example - to determine predisposition at a young age.

Allen said he probably would have laughed had a doctor told him he'd become a heavy pot smoker, but he said the information could be valuable for parents.

"'He's gonna be susceptible or more open to a marijuana addiction,' well, then, parents can start educating at a young age," Allen said.

Roache said additional studies are needed to understand what the genes do and how they're at play.

"Some genes might put you at risk for experiencing positive, rewarding effects of taking drugs," he said. "Some genes may put you at risk for greater likelihood of taking the drug in the first place... or another gene might put you at risk of not experiencing harmful side effects so you're more likely to use it."

He said the study could also lead to medications to treat, prevent or reverse marijuana dependency.

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