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Teen Marijuana Use in the New Era of Legalization


Does Legalization Mean Adolescents Think Marijuana is Harmless?

“Marijuana is the most commonly used illicit drug in the United States.”

That’s the first sentence in the article “Marijuana Legalization And Historical Trends In Marijuana Use Among US Residents Aged 12–25: Results From The 1979–2016 National Survey On Drug Use And Health.” That sentence – and others that say the same thing with slightly different words – also appears on websites about drug use and misuse maintained by the National Institutes of Health (NIH), such as the Substance Abuse and Mental Health Services Administration (SAMHSA) page about marijuana.

Here’s the introduction to the SAMHSA marijuana page:

“Marijuana is the most commonly used illegal substance in the U.S. and its use is growing. Marijuana use among all adult age groups, both sexes, and pregnant women is going up. At the same time, the perception of how harmful marijuana use can be is declining. Increasingly, young people today do not consider marijuana use a risky behavior.”

This article will identify and discuss trends in teen marijuana use over the past several decades, with a focus on how the movement toward legalization in the U.S. impacts not only marijuana use among teens and young adults, but also affects attitudes towards marijuana and marijuana use. We’ll examine results published in several peer-reviewed journal articles on marijuana prevalence and perceived risk, and present statistics related the assertion by SAMHSA that “young people today do not consider marijuana use a risk behavior.”

In addition, we’ll address several topics that adolescents and young adults might not understand completely, such as:

  • The consequences of marijuana use on the adolescent body
  • The consequences of marijuana use on the adolescent mind
  • Social, academic, employment, and other long-term consequences of adolescent marijuana use

We’ll start with a brief summary of marijuana legislation in the U.S., with a focus on the recent trend toward legalization for both medical and recreational use.

Marijuana Laws: Where We Started, Where We Are Now

The history of legislation around marijuana is neither long nor exceedingly complex.

Here’s where we started:

  • Marijuana Tax Act (1937): Regulated the import, cultivation, possession, and sale of marijuana
  • Boggs Act (1952): Set sentencing guidelines for a first offense for marijuana possession at 2-10 years in jail and a fine of up to $20,000
  • Narcotics Control Act (1956): Increased penalties for most illegal drugs, including marijuana
  • Controlled Substance Act (1970): Categorized marijuana as a Schedule 1 narcotic
  • Anti-Drug Abuse Act (1986): Enacted new mandatory minimum sentences for drug offenses, including marijuana

Here’s where we are now:

  • 1970s: Decriminalization of marijuana in 14 states
  • 1990s: Medical marijuana legalized in 21 states
  • 2012-2022: Colorado and Washington legalize recreational marijuana use in 2012, and many states follow.

As of 2022, 19 states and Washington, D.C. have legalized recreational marijuana for people over 21, and 38 states and Washington, D.C. have legalized medical marijuana. This means that for teenagers, marijuana is still illegal everywhere in the United States. However, it’s unrealistic to think the trend towards legalization for recreational use has no impact on teenagers: legal marijuana is now part of the world most teenager live in. It’s also unrealistic to think that legalization does not affect rates of marijuana use among teenagers.

But those are just our common-sense judgments about what we think is realistic or unrealistic: to confirm or refute what we think, let’s check the evidence to see what’s actually verified about teen marijuana use by concrete data published by reputable scientific journals.

Has Legalization Increased Teen Marijuana Use?

A study published in 2021 called “Recreational Marijuana Legalization and Use Among California Adolescents: Findings From a Statewide Survey” asks that exact question, but with a narrow focus on the state of California. But keep in mind that when we say narrow and California in the same sentence, that may be somewhat misleading: the survey analyzed responses from close to 3.5 million 7th, 9th, and 11th graders who answered questions in the California Healthy Kids Survey from 2010-2011 to 2018-2019. That’s a large sample set, and allows us to draw inferences relevant to the rest of the country.

The survey asked teens about past month marijuana use and lifetime marijuana use with these two questions:

Have you ever used marijuana?
Have you used marijuana in the last month?

Here’s what they found:

  • Marijuana use increased for 7th, 9th, and 11th graders between 2017 and 2018
  • Marijuana use increased for 7th, 9th, and 11th graders between 2018 and 2019
  • The largest increases occurred for:
    • 7th graders, as compared to 9th and 11th graders
    • Females, as compared to males
    • Non-Hispanic and White youth, compared to Hispanic, African-American, and multi-racial youth

This survey is important to pay attention to because California was among the first states to legalize the recreational use of marijuana. Also – given that the population is diverse, with wide variation in attitudes towards marijuana – California is traditionally known for progressive views on social and political topics. With that said, the data in this study show that legalization of recreational marijuana resulted in an increase in teen marijuana use.

There’s context to consider here, though. The long-range study we introduce at the beginning of this article shows the following data for all people in the U.S. age 12-25:

  • Declines in marijuana use between 1979-1992
  • Increases between 1992-2001
  • Decreases between 2001-2006
  • Increases between 2006-2016

According to the researchers:

“The period effect was positively and significantly associated with the proportion of people covered by Medical Marijuana Laws, but was not significantly associated with the Recreational Marijuana Laws.”

The California study identified its trends in the period directly after the time period this long-range study examined. We decided to check the national data on a related subject: whether there have been similar changes in how teenagers think about marijuana use.

Monitoring the Future: What do Teen Think About Marijuana Use?

The National Institutes of Health (NIH) and the National Institute on Drug Abuse (NIDA) conduct a large-scale, nationwide survey of nicotine, alcohol, and drug use among high school students, college students, and young adults in the U.S. every year called The Monitoring the Future Survey. Researchers at the University of Michigan conduct the survey, which includes data collected from over 50,000 8th, 10th, and 12th graders across the nation.

They gather  information on alcohol, tobacco, and drug use, but they also ask questions about attitudes towards drug use, such as:

Do you approve or disapprove or disapprove of marijuana use?
Do they think marijuana use is harmful to your health?

We’ll offer the statistics on the answers to those two questions now, from the years 2006 and 2019. Here’s what the MTF data indicates:

In 2006:

  • 82% of 8th graders strongly disapproved of marijuana use
    • 51% thought marijuana use was harmful to their health
  • 72% of 10th graders strongly disapproved of marijuana use
    • 40% thought marijuana use was harmful to their health
  • 68% of 12th graders strongly disapproved of marijuana use
    • 33% thought marijuana use was harmful to their health

In 2019:

  • 69% of 8th graders strongly disapproved of marijuana use
    • 35% thought marijuana use was harmful to their health
  • 56% of 10th graders strongly disapproved of marijuana use
    • 40% thought marijuana use was harmful to their health
  • 46% of 12th graders strongly disapproved of marijuana use
    • 15% thought marijuana use was harmful to their health

Those numbers tell the story: perceived risk of harm from and disapproval of marijuana use have declined dramatically since 2006. That tells us we need to make sure teens, parents, and anyone involved in the life of a teen knows about the risks of marijuana use. We’ll offer that quick refresher course now.

Risks of Marijuana Use: Body, Brain, and Quality of Life

In the study Adverse Health Effects of Marijuana Use, Dr. Nora Volkow, an addiction researcher who is now the Director of the National Institute on Drug Abuse (NIDA), outlines the consequences of both short-term and long-term marijuana use.

Here’s what the evidence indicates about the health effects of marijuana use, with a focus on the impact on adolescents.

Consequences of Short-Term Marijuana Use

  • Impaired short-term memory:
    • This creates problems learning and retaining information
  • Impaired motor coordination:
    • This affects reflexes the ability to operate automobiles, and increases risk of injury
  • Altered judgment:
    • This increases the chance of engaging in risky behavior, including sexual activity
  • High doses of marijuana may trigger paranoia and/or psychosis

Consequences Of Long-Term or Heavy Marijuana Use

  • Addiction (cannabis use disorder):
    • Occurs in 9% of users overall
    • Occurs in 17% of those who begin use in adolescence
    • Increases to 25 to 50% for people who use marijuana daily
This phenomenon is strongly associated with initial marijuana use early in adolescence.
  • Altered brain development:
    • Impaired neural connectivity
    • Decreased alertness and self-awareness
    • Impaired learning and memory
    • Impaired executive function
    • Decreased impulse control
    • Decreased decision-making ability
The negative effects of marijuana use on brain development is amplified if use starts in adolescence or young adulthood
  • Impaired educational outcomes
  • Increased likelihood of dropping out of school
Impaired educational outcomes and school dropout rates are strongly associated with initial marijuana use early in adolescence
  • Cognitive impairment and decreased IQ
Cognitive impairment and attenuated IQ are strongly associated with initial marijuana use early in adolescence
  • Decreased life satisfaction and vocational achievement
Quality of life and attenuated vocational achievement are associated with initial marijuana use early in adolescence
  • Symptoms of chronic bronchitis
  • Elevated risk of chronic psychosis in people at-risk of developing psychotic disorders such as schizophrenia

To support the evidence presented in the paper, Dr. Volkow rated the relative strength of the evidence supporting each marijuana-associated effect above. Here’s what she determined.

Marijuana Health Effect and Overall Level of Confidence in Evidence

  • Addiction to marijuana and other substances: High
  • Abnormal brain development: Medium
  • Progression to use of other drugs: Medium
  • Schizophrenia: Medium
  • Depression or anxiety: Medium
  • Diminished lifetime achievement: High
  • Motor vehicle accidents: High
  • Symptoms of chronic bronchitis: High

Overall, that’s a persuasive set of data that reiterates something it appears high school students no longer understand: there are significant risks associated with initiating marijuana use during adolescence, including risks to the brain, the body, and long-term quality of life. We encourage parents to share this information with teens, and to remind themselves of this information if they’re tempted to minimize the risks of marijuana as a result of the recent trend towards legalization.

We have one more study to share – and this one is very important for parents.

Initiation of Adolescent Marijuana Use: What Role Does Parental Supervision Play?

Published in 2020, the article “Identifying Sensitive Periods When Changes In Parenting And Peer Factors Are Associated With Changes In Adolescent Alcohol And Marijuana Use” contains information that we consider mandatory reading for parents of teens who may be at-risk of experimenting with alcohol or marijuana.

Researchers collected data from 503 adolescent boys who attend public schools in Pittsburgh, PA and administered questionnaires about their home and peer life. Here are the two primary questions they sought to answer:

Are changes in parenting and peer factors associated with changes in adolescent marijuana and alcohol use?
Are there sensitive periods when changes in parenting and peer factors are more strongly associated with changes in adolescent marijuana and alcohol use?

Here’s what they found:

  • Reduced parental supervision correlates with increased frequency of marijuana use
  • Reduced parental supervision correlates with increased frequency of alcohol consumption and increased amount of alcohol consumed
  • Increases in peer delinquent behavior correlate with increased marijuana and alcohol use
  • Increases in peer drug use correlate with increased marijuana and alcohol use
  • Increased parental stress correlates with increased marijuana and alcohol use
  • These relationships were strongest at ages 14 and 15, and decreased toward the end of adolescence

That data needs no interpretation.

Therefore, we can cut straight to the chase.

While many parents are tempted to lean back during the teen years, meaning they may want to decrease their level of supervision, involvement, and direct engagement with their teen, this can have negative consequences.

We suggest leaning in.

It’s true: teens often walk, talk, and act just like adults. They’re smart. They’re clever. Some are full-grown by adolescence – except for their brains. A teen can do calculus and physics and write amazing essays in AP English. Yet their brains lack a fully developed prefrontal cortex, which is responsible for regulating behavior, rational decision-making in the moment, and impulse control. In 2022, a teen may see the trend toward marijuana legalization and think:

“Well, they made it legal. Is it really all that bad?”

Their brain may run with this idea – absent a fully developed prefrontal cortex – and end up making a decision that has significant negative consequences. If they repeat that decision, and engage in chronic marijuana use, that decision may impact the health of their body and brain in the short-term, and impact their quality of life in the long-term.

When we say lean in, we don’t mean parents need to hover over their teens like parents of toddlers on the first trip to the playground. Rather, we mean stay engaged, stay focused on parenting, and know the details about important things in their lives: who their friends are, where they’re going, and what they’re doing.

Teens don’t love being watched 24/76 by their parents, but they do love knowing someone is watching out for them. We hope that makes sense to parents reading this article, because it’s an important part of parenting a teen. Parents can be present without being overbearing. It’s a delicate balance, but it’s possible. That balance between supervision and freedom is something every parent needs to find for themselves and their family.

For parents who think their teen may be at-risk of experimenting with marijuana, we recommend erring on the side of supervision. For parents who think their teen has moved the experimental phase and actively abuses marijuana, we recommend arranging a full psychiatric evaluation and assessment for substance use disorder.

We’ll end this article with something we tell parents all the time. Not because we like to hear ourselves talk, but because it’s supported by decades of evidence:

The sooner a teen with a substance use disorder receives treatment, the better the outcome.

Finding Help: Resources

If you’re worried about teen marijuana use and seeking treatment for your teen, please navigate to our page How to Find the Best Treatment Programs for Teens and download our helpful handbook, A Parent’s Guide to Mental Health Treatment for Teens.

In addition, the American Academy of Child and Adolescent Psychiatry (AACAP) is an excellent resource for locating licensed and qualified psychiatrists, therapists, and counselors in your area. Both the National Institute of Mental Health (NIMH) and the National Alliance on Mental Illness also provide and high-quality online resources, ready and waiting for you right now.

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