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Marijuana Research Review

A Washington University School of Medicine in St. Louis Survey of 216,000 adolescents from all 50 states reveals marijuana-related problems among teens are declining.


A press release from the medical school of the University of Washington in St. Louis reports that the use of marijuana by teenagers has declined in recent years, despite the legalization and decriminalization of the drug in many states. Researchers at the school surveyed more than 200,000 teens in 2002 and again in 2013. They found a 24 percent decline in marijuana-related problems and a 10 percent decline in overall marijuana usage.

In 2002, just over 16 percent of those 12 to 17 reported using marijuana during the previous year. That number fell to below 14 percent by 2013. Meanwhile, the percentage of young people with marijuana-use disorders declined from around 4 percent to about 3 percent.

These results are noteworthy in a time when marijuana is becoming increasingly tolerated by the law. Many opponents of legalization have worried that greater access to the drug will lead to widespread usage and abuse. Supporters of legalization, on the other hand, argue that a culture of legality will lead to more responsible usage of marijuana.

The authors of this study do not believe their results have anything to do with legalization, however. They point out instead that children with behavioral problems are more likely to wind up use marijuana and other drugs during adolescence. Their data also shows a decline in childhood behavioral problems, and the researchers think this is more likely the cause of the decline in drug use. Richard A. Grucza, one of the researchers, explains:

We were surprised to see substantial declines in marijuana use and abuse. We don’t know how legalization is affecting young marijuana users, but it could be that many kids with behavioral problems are more likely to get treatment earlier in childhood, making them less likely to turn to pot during adolescence. But whatever is happening with these behavioral issues, it seems to be outweighing any effects of marijuana decriminalization.

Other research shows that psychiatric disorders earlier in childhood are strong predictors of marijuana use later on. So it’s likely that if these disruptive behaviors are recognized earlier in life, we may be able to deliver therapies that will help prevent marijuana problems—and possibly problems with alcohol and other drugs, too.

The authors of the study do not speculate as to the cause of the decline in behavioral problems.

Other research bears out the study’s findings that decriminalization and legalization has not led to widespread marijuana abuse by teens.

The federal Substance Abuse and Mental Health Services Administration surveyed marijuana usage during roughly the same timeframe. They found a small decline in usage in the past year by respondents aged 12 to 17, from 15.38 percent to 13.86 percent between 2002 and 2012. They also found that young adults—aged 18 to 25—are twice as likely as teens to have used marijuana in the last year: their usage rate increased from 29.13 percent to 31.12 percent.

In Colorado, where recreational marijuana is legal, a November 2015 poll found that 53 percent believe legalization has been good for the state, while 39 percent believe it has been bad. The most common complaint is from law enforcement, which does not yet have standards in place to enforce the safe use of the drug. For example, there’s currently no reliable test to determine if a person is too intoxicated from marijuana to drive a car.

One clear consequence of legalization in Colorado has been a steep decline in marijuana-related arrests. In 2011 there were 39,027 marijuana court cases in the state and only 2,036 in 2014. Christopher Ingraham at the Washington Post says:

Those 37,000 fewer cases represent a savings of untold millions of dollars in court costs and law enforcement fees. They represent 37,000 fewer people who have to deal with the stigma and financial burden of an arrest and possible conviction. They represent countless police man-hours able to be devoted to other tasks.

Questions for Reflection and Discussion

  1. How do you feel about marijuana legalization? What do you think is the best reason for or against legalization?
  2. Are you surprised that decriminalization and increased access to marijuana has not led to a surge in usage by teens?
  3. Do you expect more states to legalize marijuana in the future?
  4. How would you advise teenagers about marijuana use?


  1. As the United States becomes increasingly tolerant of marijuana, usage of the drug by teens has actually declined.
  2. Researchers say the decline in teen marijuana use was likely caused by a decline in childhood behavior problems, unrelated to legalization. However, it’s noteworthy that legalization has not led to an increase in teen drug use.
  3. There is still significant public disagreement about whether marijuana legalization is a good idea, including in states where the drug is already legal. Currently, a small majority of Americans are in favor of legalization.
  4. The issue of marijuana as a gateway to harder drugs should be further studied.
  5. Warning younger persons about marijuana from a negative perspective is not as helpful as a positive consideration of life choices—of all factors in a healthy lifestyle.

Peter Bass
© 2018 CYS


Jim Dryden (2014). “As more states legalize marijuana, adolescents’ problems with pot decline.” Washington University School of Medicine in St. Louis News, May 24.

Christopher Ingraham (2015). “After legalization, Colorado pot arrests plunge.” The Washington Post Wonkblog, March 26.

Christopher Ingraham (2015). “Legal weed having little effect on teen marijuana use, federal data shows.” The Washington Post Wonkblog, December 18.

Joshua Miller (2016). “In Colo., a look at life after marijuana legalization.” The Boston Globe, February 22.

National Survey on Drug Use and Health: Comparison of 2002-2003 and 2011-2012, Table 2: Marijuana Use in the Past Year.

David Olinger (2015). “Colorado pot critic’s report suggests bad side effects of legalization.” The Denver Post, September 14.

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