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New Study Shows Increase in Chronic Marijuana Use in Legalized States

  Teen blowing smoke out of their mouth after smoking a marijuana joint

Across the country, 11 states as well as Washington D.C. have legalized recreational marijuana use. Likewise, medical marijuana use is legal in 33 states and D.C. A new study published in JAMA Psychiatry in November took a look at the effects and impacts of the legalization of recreational marijuana on use patterns and cannabis use disorder across age groups.

This new marijuana study sought to shed light on the effect of states that have legalized marijuana and take a closer look at marijuana use in teens. Looking at usage following marijuana legalization from 2012 to 2015, researchers found:

  • Problematic marijuana use in teens aged 12 to 17 was 25% higher compared to states that didn’t have legal recreational use. There wasn’t a change in the prevalence of frequent use or past month use among teens.
  • Among adults 26 and older, the rate of past-month marijuana usage was 26% higher than in the states without recreational legalization. Past-year problematic use went up by 37%.
  •  Among young adults 18 to 25, there was no difference in past-month, problematic or frequent marijuana use.

Magdalena Cerda, who was the study’s lead author, said the findings suggest as more states move toward legalizing recreational marijuana use, there should also be a focus on the prevention of substance use and treatment to prevent unintended negative consequences.

The study analyzed data from the National Survey on Drug Use and Health and represents a sample of nearly 505,800 respondents. Investigators focused attention on Colorado, Washington, Alaska, and Oregon, which were the first four states in the country to legalize recreational marijuana. They tracked trends in the use of marijuana both before and after legalization and compared trends in these states to trends in states that hadn’t legalized recreational marijuana use.

Teenage Marijuana Use Statistics

Generally looking at teenage marijuana statistics, according to the U.S. Department of Health & Human Services, it is the most commonly used substance among adolescents after alcohol. According to HHS, fewer adolescents believe marijuana use could be harmful than in the past. In 2016, HHS found that five percent of students in the 8th grade said they had used marijuana at least once in the past month. That went up to 14% of 10th graders and 23% of 12th graders.

Also, the current use of marijuana has gone up among adolescents in the past ten years for students in the 12th grade, while rates for drinking and alcohol use have gone down.

As far as teens addicted to marijuana, it’s possible that many young people believe marijuana isn’t addictive. According to the National Institute on Drug Abuse, it is. They estimate that around 9% of users become addicted to marijuana. The number goes up for people who start young and for daily users. For example, one in six who start using marijuana at a young age may become addicted, and around 20% to 50% of daily users may develop an addiction.

Effects of Marijuana on Teens

The effects of marijuana on the teenage brain can be more severe and pronounced than the effects on older people. According to the Centers for Disease Control and Prevention, during the teen years, the brain is still actively developing. The brain isn’t fully developed until the mid-20s, which is why marijuana can be especially detrimental for adolescents. Some of the potential dangers of marijuana use in teens include:

  • Lowered school performance
  • Mental health problems including anxiety and depression
  • Impaired driving
  • Increased potential for addiction

Signs of Teen Marijuana Abuse

When parents know what to look for in terms of the signs of teen marijuana abuse, they may be able to intervene earlier. One of the earliest signs of teenage drug use of any kind is a change in behavior. This could manifest as changes in friend groups or defensiveness and anger when confronted. A teen using marijuana may withdraw from activities with family and loved ones, and there may be a breakdown in communication.

A teen may show signs of a loss of judgment. There can be slurring of speech, and many teens who use marijuana may start skipping class or have declining grades and school performance.

If you believe your teen is struggling with marijuana or substance use, contact Next Generation Village to learn about treatment options and programs.


Science Daily. “In states where recreational marijuana is legal, problematic use increased among adults and teens.” November 13, 2019. Accessed December 30, 2019.

U.S. Department of Health & Human Services. “Marijuana Use In Adolescence.” Accessed December 30, 2019.

National Institute on Drug Abuse. “Is It Possible for Teens to Become Addicted to Marijuana?” January 2014. Accessed December 30, 2019.

Centers for Disease Control and Prevention. “Marijuana Use and Teens.” April 13, 2017. Accessed December 30, 2019.

Ali, Shahid et al. “Early detection of illicit drug use in teenagers.” Innovations in Clinical Neuroscience. Accessed December 30, 2019.

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