Medical Marijuana May Improve Cognitive Function, Study Says

Unlike recreational users, medical patients saw brain benefits.
Photo via iStock/Nicholas Belton

Photo via iStock/Nicholas Belton

A new study says medical marijuana, unlike recreational marijuana, may actually improve cognitive functioning in adults, rather than impair it.

The study, led by McLean Hospital’s Staci Gruber and published in Frontiers in Pharmacology, found that after three months of medical marijuana treatment, patients performed certain cognitive tasks better than they did before treatment began. Specifically, Gruber explained in a statement, they saw improved performance in skills managed by the frontal cortex, which is responsible for thinking, problem solving, and planning.

Medical marijuana also appeared to improve patients’ underlying conditions, sleep, and overall health. Notably, it also helped to wean some participants off opioid pain medications.

“They don’t have the degree or the severity of pain that they have without the medical marijuana on board,” Gruber says. “[They say,] ‘I don’t need Oxy anymore—I have this. Given the national epidemic, I think it’s something that bears far greater scrutiny.”

The study was small—only 11 people participated in both baseline and three-month testing—but such results are striking. They also raise a question: How can medical marijuana affect the brain positively, while recreational marijuana does the opposite?

It’s perhaps because the drugs are formulated differently. Medical marijuana is typically low in THC, the compound responsible for the drug’s psychoactive properties, and high in other cannabinoids. The reverse is true of most strains sold on the street. Such a discrepancy, as well as differences in use patterns, can drastically change how the drug affects the body and brain.

“It’s a complicated story because of this heterogeneity of product types and how people are using, with regard to frequency and magnitude,” Gruber explains. “A lot of it has to do with how they’re using and what they’re using.”

Age may also play a role. The average subject in Gruber’s study was 48, while most recreational marijuana studies look at adolescents.

“The brain is particularly vulnerable during adolescence and emerging adulthood,” Gruber says. “These people [in the study] are past that period of vulnerability.”

There’s still a lot Gruber, who is director of the Marijuana Investigations for Neuroscientific Discovery program at McLean, and her team don’t know, and they will continue the study for at least another two years. Indeed, Gruber says these preliminary findings are just the tip of the iceberg.

“As a clinical researcher, I’m not interested in exploring only the good or the bad, I’m only interested in the truth,” she said in the statement. “That’s what our patients and our recreational users have a right to know and a right to expect from us. People are going to use it. It’s up to us to figure out the very best and safest ways in which they can do that.”


Jamie Ducharme Jamie Ducharme, Contributor jducharme@bostonmagazine.com