Wednesday, September 14, 2016

Marijuana and the Teen Brain

Randi Schuster
Randi Schuster, PhD, a postdoctoral fellow at the Center for Addiction Medicine

With Election Day right around the corner, the legal landscape for marijuana in the United States is poised to change yet again. Marijuana is currently legal for recreational use in four states and for medicinal use in 25 states (plus the District of Columbia). On November 8th, five more states, including Massachusetts, will decide whether to legalize recreational use and another four will vote on medical use.

Perceived Harm of Marijuana Use Is Decreasing

This trend toward legalization signals a related decrease in the perceived harm of using marijuana. According to Randi Schuster, PhD, a postdoctoral fellow with the Center for Addiction Medicine at Massachusetts General Hospital, this is cause for concern.

“This decrease in harm perception, which is currently at its lowest point in the last 40 years, often precedes an increase in use,” Dr. Schuster explained at a presentation on marijuana legalization presented as part of Mass General’s National Recovery Month program.

After alcohol, marijuana is the most commonly used drug in the United States, with nearly half of adults reporting having used it at some point in their lives. Regular users are most highly concentrated among young people 18 to 25—nearly one in five young adults is a regular user (defined as those who use marijuana at least once per month)—with the next highest concentration among teens 13 to 17 years old.

How Marijuana Impacts the Teen Brain

The prevalence of marijuana use among this younger cohort is worrisome, according to Dr. Schuster. Tetrahydrocannabinol, the active ingredient in marijuana commonly known as "THC," targets the frontal lobe of the brain, which is critical for important functions like cognition and impulse control. The frontal lobe is also one of the last areas of the brain to develop, leaving teens and young adults particularly vulnerable to these effects.

Dr. Schuster’s research into the effects of marijuana on the teen brain, "Early onset marijuana use is associated with learning inefficiencies," has revealed this impact. “Non-users perform better than users in several areas of cognition—specifically areas of cognition that are important for learning and academic achievement. Things like attention, sustained attention and executive function,” Dr. Schuster said.

While there has been relatively little research examining the long-term health impacts of marijuana use, one area of research that has thus far been very consistent is the impact on young people. According to Dr. Schuster, “What the data show is that the younger you are when you first tried marijuana...the greater [your] risk for adverse consequences and worse cognitive functioning.” She continued, “We also see that younger cohorts are more likely to see abnormalities in brain structure and function.”

So while many adults perceive marijuana to be a relatively harmless drug, often because of their own past experience, this emerging data suggest a much different situation. However, it should be noted that today’s marijuana is much different from what was available the 1960’s and 1970’s—potency has risen from typical rates of 1-2% THC back then to 20-25% THC today (with certain cannabis concentrates now available even going as high as 76% THC).

National statistics on youth marijuana use suggest that higher rates of youth usage are correlated with the current legalization trends. As the marijuana landscape in the United States changes, both in terms of public policy and the biology of the plant itself, Dr. Schuster urged the audience to pause and consider the public health implications of this trend.

Learn more about the Center for Addiction Medicine at Mass General.

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