Marijuana Use and Gray Matter

 In Blog, Guest Blogs

by Mary Boudreau Conover BSNed

The data from Gilman et al 2014 studies (1) on recreational marijuana use in young adults compared to nonusing controls suggested that marijuana exposure is associated with alterations in the gray matter of the brain, particularly that of density, volume and shape. The first clue to the significance of this fact is that 95% of the blood pumped to the brain flows to the gray matter. That’s a pretty generous allotment and reflects the importance of the area served.

Consequences of Short Term Use

That would be muscle control and sensory perception. Areas in the gray matter govern perception, attention, reaction time and judgment; seeing and hearing; short-term memory, learning and decision-making; emotions, speech and self-control; balance and motor coordination. These functions play a starring role in sexual behavior, safe driving, intelligent conversation, successful intelligent lifetime choices, and educational and career pursuits. High doses may result in psychosis.(2-3)

Traffic Fatalities

The stats for traffic accidents involving young recreational marijuana users are climbing. In 2010, Columbia University researchers looked at 24,000 driving fatalities and did toxicology exams on all of them. Marijuana contributed to 12% of the deaths and that was 4 years ago! (4,5) Unfortunately, there was no mention of the associated significant, but nonfatal injuries, which can be life-altering.


In this group, vulnerability to addiction is significant and withdrawal is difficult. Adults who regularly smoked marijuana during adolescence have impaired connectivity among nerves that involve alertness, awareness, learning, memory and a significant decline in IQ compared with those who have never smoked marijuana.(6)

Down the Road a Piece…

Information from these references alerts young people to the impact use of marijuana will have on how you live your life and where it takes you. I am well acquainted with 50 and 60 year olds, who, in their wild youthful days, smoked marijuana socially, sitting around in their little groups feeling good. They tell me that it had “no lasting effects” and hasten to add that they didn’t drive until it wore off; no harm; no foul! Well, we’ve just learned that it doesn’t exactly “wear off”— not the permanent damage. All these years later, it is difficult to carry on a meaningful conversation with them.


  1. Gilman JM, Duster JK, Lee S, et al: Cannabis use is quantitatively associated with nucleur accumbens and amkygdala abnormalities in young adult recreational users, Journal of Neuroscience 34(16):5529-5538, 2014.

Note from Eva T.

Mary Boudreau Conover, retired RN, author and lecturer has been a friend of mine for over 10 years. She is a wealth of knowledge and knows how to sift through legitimate scientific studies and write about the bottom line. Eva T. Strength and Conditioning is honored to have her contribute to our list of articles that will contribute to the health and fitness of all of us and our blog followers. Thank You Mary!

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