Marijuana-Cannabis-Weed-Bud-GramFor years we have reported both scientific research on the dangers of marijuana as well as news stories and articles related to injuries and deaths caused by marijuana.

From time to time when we post this sort of information, marijuana proponents take to email and social media, telling us we need to “do some research” and “educate” ourselves. Well, we have.

Below is just some of the research published this year alone about the link between marijuana and cognitive problems.

The Research

Researchers continue to link marijuana-use with memory issues and problems related to learning.

Researchers writing in the  journal of the American Psychological Association say, “Verbal memory difficulties are the most widely reported and persistent cognitive deficit associated with early onset marijuana use. . . . Young adults reporting early onset marijuana use had learning weaknesses, which accounted for the association between early onset marijuana use and delayed recall.”1

Researchers writing in the journal Drug and Alcohol Dependence write, “frequent users were more likely to drop out of college and plan to delay graduation when compared to non-users. All marijuana user groups reported lower GPAs, on average, than non-users. . . . Students who use marijuana frequently at the beginning of the college career are especially at risk for lower academic achievement than non-users, suggesting that early intervention is critical.”2

Earlier this year, researchers published a study in the Journal of the American Medical Association, concluding, “cumulative lifetime exposure to marijuana remained significantly associated with worse verbal memory.”3

A study published in March in the Journal of Studies on Alcohol and Drugs found, “Marijuana smokers had poorer executive function . . . [and] earlier age at marijuana onset and increased marijuana use predicted poorer neurocognitive performance, and perseverative errors on the [test used in the study] significantly predicted marijuana group membership.”4


This research about the damage marijuana does to a person’s memory and cognitive abilities underscores what we have said for years: Marijuana may be many things, but “harmless” simply is not one of them.


1 Early onset marijuana use is associated with learning inefficiencies.
Schuster, Randi Melissa; Hoeppner, Susanne S.; Evins, A. Eden; Gilman, Jodi M.
Neuropsychology, Vol 30(4), May 2016, 405-415.

2 Marijuana use trajectories and academic outcomes among college students.
Cynthia K. Suerken, Beth A. Reboussin, Kathleen L. Egan, Erin L. Sutfin, Kimberly G. Wagoner, John Spangler, Mark Wolfson.
Drug and Alcohol Abuse, Volume 162, 1 May 2016, 137 – 145.

3 Association Between Lifetime Marijuana Use and Cognitive Function in Middle Age: The Coronary Artery Risk Development in Young Adults (CARDIA) Study.
Auer R, Vittinghoff E, Yaffe K, et al.
JAMA Intern Med. 2016;176(3):352-361. doi:10.1001/jamainternmed.2015.7841.

4 Marijuana Use Predicts Cognitive Performance on Tasks of Executive Function
Mary Kathryn Dahlgren M.S., Kelly A. Sagar M.S., Megan T. Racine M.Ed., Meredith W. Dreman Ed.M.. Staci A. Gruber Ph.D.
Journal of Studies on Alcohol and Drugs, 77(2), 298–308 (2016).