Mclean Hospital

The Marijuana Debate: A Conversation With Staci Gruber, PhD

August 2, 2016

For more than 20 years, Staci Gruber, PhD, director of McLean Hospital’s Cognitive and Clinical Neuroimaging Core and associate professor of psychiatry at Harvard Medical School, has dedicated her work to uncovering the mysteries of marijuana. As the country continues to debate the pros and cons of the legalization of marijuana and medical marijuana, Dr. Gruber’s work has never been more critical. She recently sat down with McLean Hospital’s news team for an exclusive interview.

What have you discovered about the impact of early marijuana use?

The results have been striking. Data from our studies and other groups have now demonstrated that chronic, heavy marijuana smokers with earlier onset (under the age of 16) show significant changes in brain structure and function relative to those with later onset. They appear to have more difficulty with cognitive tasks, particularly those mediated by the frontal cortex. Interestingly, later onset smokers don’t appear to have the same level of difficulty with frontally-mediated tasks and appear more similar to those who have never smoked.

Does the type of marijuana product used make a difference in your findings?

While we’ve looked at age of onset, frequency, and magnitude of marijuana use and done some work exploring the ways that people use cannabis (smoking, vaporizing, dabbing, edibles, etc.), there’s a lot we still have to learn. We’ve recently begun collecting information on the actual products that our subjects use. So far, we can say that earlier age of onset as well as frequency and magnitude of use are all related to task performance and measures of brain health.

What do we know about the impact of medical marijuana on brain function?

No studies thus far have assessed the specific impact of medical marijuana on brain-related measures or assessed outcome over extended periods of time. That’s why in 2014 we launched the MIND program (Marijuana Investigations for Neuroscientific Discovery). Our first phase of study involves assessing patients certified for medical marijuana use prior to the initiation of their medical marijuana treatment using a comprehensive battery of measures that captures information regarding their mood, cognitive status, quality of life, sleep, clinical symptoms, and their current use of ‘standard’ pharmacologic agents. We’ve collected data on brain structure and function as well as their most commonly used products and will continue to see them for follow-up visits over the course of 12 months. While our data are very preliminary, early findings are promising, as the majority of our participants report a positive experience with the treatment.

fMRI image of healthy controls (A) vs MJ smokers (B) completing an inhibitory task. Early onset smokers (C) activate a different area relative to late onset smokers (D) who look more similar to controls with regard to regional activation patterns.

Why is marijuana research so critical at this point in time?

Perception of risk and harm related to marijuana use is at an all-time low among our youth, which may in fact be the result of our ongoing dialogues about medical marijuana. In fact, for the first time in 2015, the National Monitoring the Future study reported that more high school seniors smoke marijuana every day than smoke cigarettes. It is important to let them know that during adolescence and teen years, the brain is still developing and vulnerable to many influences, including drugs. In addition, more potent, concentrated forms of marijuana like shatter, wax, dabs, and budder are increasing in popularity and may be more likely to cause negative effects in those who are still developmentally immature, given the very high levels of THC in these products. My work and that of my colleagues in this field is dedicated to answering many complicated questions that are designed to help policymakers make sound, fact-based decisions.

Dr. Gruber’s work has recently been featured on CNN, Yahoo News, ESPN, and PBS.

August 2, 2016

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