There has been a great deal of discussion about the use of alcohol by adolescents recently. It is great that the town is talking about these things, but alcohol is not the only potentially addictive substance that is available for adolescents to use today. The use of cannabis-related substances is growing rapidly, and cannabis may pass alcohol as the substance of choice for many young people in the near future.
In doing the background research for this column, I became aware that public health professionals are no longer using the term “recreational cannabis.” I learned it is being replaced by the term “adult use cannabis.” As a volunteer elected to a very small board in a small town, I might have missed the memo on the vocabulary change, but I will use the new term in the future. From my perspective, however, that change is probably appropriate if indirect recognition that the ideal of relatively consequence-free highs from cannabis use that was promoted early in the legalization process may, in retrospect, have been a bit oversold by its proponents. There are many differences between alcohol and cannabis, but they both potentially can cause serious harm to the maturing brain, and therefore we should try to understand the risks involved in their use.
Today, adolescents and young adults generally perceive cannabis as less harmful than alcohol. That is debatable. With significantly increasing potency of and vastly greater variety of products available, cannabis-related emergency department visits, hospitalizations for cannabis use disorder, and unintentional ingestions (especially by young children) have all increased. The long-term effects of heavy and frequent cannabis use in adolescents are now known to include significant cognitive impairment, increased risks of psychotic breaks and the broader development of cannabis use disorder.
In short, the long-term consequences of cannabis and alcohol seem to be variations on a common theme., i.e., as the adolescent brain matures into adulthood, it is particularly vulnerable to disruptions caused by substances that might be relatively benign when used in moderation by an adult.
My understanding of that theme has been markedly strengthened by a neuroradiology study designed by a University of Vermont psychiatrist (Matthew Albaugh) which was published in the journal with the interesting title “Molecular Psychiatry.” The figure below represents my interpretation of the basic results of that study and their relevance to public health science.
Since 2010, eight European medical centers have collaborated to study brain development using MRI and other techniques. Albaugh used data from that collaborative to evaluate the impact of cannabis on the neurodevelopment process.
The study population of 704 individuals had been followed for 10 years. Every participant had three MRI measurements of the architecture of the cortex of their brains during that time. (The prefrontal cortex is the area of the brain behind the forehead which is responsible for higher cortical and executive functions like planning, prioritizing and decision making.)
The study population was divided into three groups. One was those who were regular and consistent cannabis users from their early teen years. The second had delayed all cannabis use until young adulthood (defined in the paper as age 19-22 years), The third contained only individuals who reported no cannabis use during the entire period.
On the graph, the average cortical thickness of the early and constant users (who started early) is shown by the solid line. The dimensions of the young adult initiators (started late) are shown by the grey dashed line and dotted line that describes the “never users.”
The early users show a meaningful thinning of the cortex. That is not much of a surprise. There is a substantial body of research that shows that cortical thinning is a common result of heavy substance use in adolescence. There are many papers that demonstrate that for both alcohol and cannabis. But the comparison of that result with the dashed line describing the dimensions of the group that delayed cannabis use by five years is potentially very significant. The later-starting brain seems much more able to tolerate the challenge of cannabis than that of the early starters. And the fact that there is very little difference between the late starters and the never users is also surprising and meaningful. Apparently, once the brain matures, it might be more resistant to substance challenges.
No study is perfect; they all have limitations. Self-reporting of health data always carries risks — especially for young individuals over a 10-year period. We should always be careful about overextending the conclusions of a very focused and technical experiment. The initial MRIs were done before 2013 and being an adolescent today is very different from adolescence in 2013. The European dope of 2013 may be very different from that in the cannabis brownies of 2025. But even with all of those limitations, I don’t think you need a medical degree to want your children and/or grandchildren to have as robust a frontal cortex as possible, and therefore many readers looking at that graph might pause and think for a minute. And perhaps more than a few might wonder what they should expect from their elected and appointed officials to help them deal with these issues in today’s complex world.
The primary goal of this column was to try to introduce the community to the complexity of cannabis use especially for adolescents. I hope my presentation of it was understandable and helpful. If there are questions or comments, please email me at thomasmassarombhd@gmail.com.
Dr. Tom Massaro is chair of the Board of Health and also serves on the Town Charter Committee. He is an emeritus professor at the University of Virginia where he practiced medicine and taught public health, health law and the business of medicine for many years. He lives in Marblehead with his wife and son. He is not writing for the Board of Health.
