Last updated: September 25, 2023
According to a Monitoring the Future survey, marijuana use among 8th, 10th and 12th graders has remained steady over the years, but perceptions of its risk has decreased. That may soon change and maybe the use itself is the reason!
Marijuana has over 19.8 million users and is the most commonly used illicit drug in the country. In 2013, the National Survey on Drug Use and Health (NSDUH) found that 81 percent of drug users have used marijuana within the past 30 days and 64.7 percent have solely used marijuana. Researchers from the University of Texas’ Center for Brain Health and the Mind Research Network have found that regular marijuana users have a lower brain volume (though higher brain connectivity) than non-users. It seems that smoking “dope” means smaller brains.
In the study “Long-term effect of marijuana use on the brain”, researchers found that regular users of the drug have less gray matter in their orbitofrontal cortex (OFC). This is the region of the brain that controls motivation, decision-making, and addictive behaviors. The team of researchers, led by Dr. Sina Aslam, studied 48 adult marijuana users aged 20 to 36 who used the drug on average three times a day, and compared them to non-users. They combined three different MRI techniques to monitor the change in brain size and activity.
Dr. Aslam’s team found that though the OFC is losing its gray matter, marijuana users seem to have a higher connectivity between neurons in this part of their brain, and the longer the marijuana use, the greater the connectivity. Until the “wiring” starts to degrade, that is—after six to eight years of prolonged use. It’s also unclear whether stopping marijuana use can reverse the effects and whether occasional users experience the same effect. They believe this higher connectivity is the brain’s way of compensating for its loss of gray matter. The concentration of neurons doesn’t appear to lead to greater concentration, however, especially when under the influence of the drug!
The OFC is one of the least understood regions of the brain, located in the frontal lobe, right behind the eyes. It’s responsible for sensory integration and decision-making, but primarily it plays a large role in comparing the expected rewards/punishment of a situation and the actual delivery of it. Therefore, it serves as an important site of adaptive learning. Gray matter in this region is responsible for monitoring muscle control and sensory perception, such as speech, decision-making, and self control. Impairment to this region is associated with substance abuse and other addictive behaviors.
Previous studies on the effects of long-term marijuana use have been inconclusive. This is the first time researchers have been able to determine a direct link between these changes in the brain and a user’s frequency of use. Some challenges still remain. The paper’s authors admit that it is still too early to say whether the decrease in gray matter in the OFC is completely due to marijuana use. Those with a smaller orbitofrontal cortex at the age of 12 is more likely than others to start using marijuana. A deficit in this region impairs self-control and predisposes one to addictive behaviors. Therefore, it is possible that some underlying condition is what’s causing both the decrease in gray matter and the increase in marijuana use.
While these findings do not discredit the benefits of medical marijuana use for diseases such as glaucoma or Tourette’s, they do give pause to the recreational pot smoker. With 23 states having legalized medical marijuana, it seems this is a research area that will soon be revisited. With their smaller brains, it probably won’t be pot heads!