Since the 1960s, teen marijuana use has been a significant concern among parents and public policymakers, not only for the basic health reasons – substances of misuse are bad for your body – but also for the potential negative mental health consequences of early marijuana use.
A new study called “Trends in Marijuana Use among Adolescents in the United States” addresses this concern by analyzing the trajectory of teen marijuana use over the past ten years. Understanding this trend is important to us for the reasons we state above: the implications for teen physical and mental health.
It’s our job to keep current with the latest developments and trends that impact teens and young adults, and this new study is particularly relevant as parents and policymakers around the country fear the recent trend toward legalization of recreational marijuana may lead to increased use among teens.
It’s a valid fear, considering the fact that most recent studies on marijuana use among teens indicate that, compared to period from 1960-2010, most teens don’t believe marijuana use is a serious risk to their physical or mental health.
Before we look at the results of the new study, we’ll look back that the trends in marijuana use among teens and young adults going back to 1979, the first year we initiated data collection on marijuana use nationwide.
Trends in Marijuana Use: Late 1970s – Late 2010s
A comprehensive meta-analysis on this topic shows the following trends in marijuana use among adolescents and young adults in the U.S between 1979 and 2016:
- 1979-1992: marijuana use decreased
- 1992-2001: marijuana use increased
- 2001-2006: marijuana use decreased
- 2006-2016: marijuana use increased
Now we’ll look at a survey that focuses on our state, California, which reports these developments:
- 2017-2018: marijuana use increased
- 2018-2019: marijuana use increased
- 2017-2019: significant increase for females and white youth
California was one of the earliest states to decriminalize recreational marijuana use, which makes this report important, since it covers the period immediately following legalization. It also brings us to the present moment: legalization occurred in California almost ten years ago, with another ten states following close behind.
That means there’s been time for trends to establish themselves, and for us to analyze those trends to understand how we can best support our teens and young adults. It’s important to understand the consequences of early marijuana use, which we’ll now review.
The Consequences of Teen Marijuana Use on Physical and Mental Health
Dr. Nora Volkow, chief scientist at the National Institute on Drug Abuse (NIDA), published a study in 2016 on the negative health consequences of marijuana use, which she initiated in order to create a reliable source of data regarding the impact of marijuana use on overall health. Here’s how she describes the need for and the goal of this publication:
“…multiple studies have reported detrimental effects [of marijuana use], others have not, and the question of whether marijuana is harmful remains the subject of heated debate. Here we review the current state of the science related to the adverse health effects of the recreational use of marijuana, focusing on those areas for which the evidence is strongest.”
Data from 77 papers on the impact of marijuana on health showed the following short-term negative consequences of marijuana use, i.e. what happens in the hours immediately following use:
- Impaired short-term memory
- Impaired motor coordination
- Altered judgment
- May trigger paranoia and/or psychosis
Data from the same sources showed the following long-term consequences of marijuana use, i.e. what happens when an individual uses marijuana over a long period of time. Chronic, heavy marijuana use is associated with:
- Addiction to marijuana and other substances
- Impaired brain development
- Decreased academic achievement
- Decreased vocational achievement
- Increased high school dropout rates
- Decreased IQ
- Reduced cognitive function
- Decreased quality of life
- Chronic bronchitis
- Increased risk of psychosis
In addition, Dr. Volkow offered an assessment of her “level of confidence for the evidence” about the adverse effects of teen marijuana use on health and wellbeing:
- Cannabis use disorder: High confidence
- Substance use disorder, non-cannabis: High confidence
- Impaired neurological development: Medium confidence
- Recreational use of additional substances: Medium confidence
- Schizophrenia: Medium confidence
- Depressive disorders: Medium confidence
- Anxiety disorders: Medium confidence
- Impaired work and academic accomplishment: High confidence
- Increased involvement in car crashes: High confidence
- Increased lung problems: High confidence
Now, with all that information in mind – the trend data and the physical/mental health data – let’s take a look at the study we introduce in the beginning of this article and learn whether the recent trends in legalization have led to increased or decreased marijuana use among teens.
Ten Year Trends in Teen Marijuana Use
To gather data for this report, researchers used information published between 2011 and 2021 in the Youth Risk Behavior Survey (YRBS), which administers the YRBS to high school students every two years. For this study, the total sample set included data on 88,313 high school students surveyed in 2011, 2013, 2015, 2017, 2019, and 2021.
Researchers focused on answers to the following questions:
Have you ever used marijuana?
Did you use marijuana before age 13?
Have you used marijuana in the past 30 days?
Here’s what they found:
Ever Used Marijuana
- 2011: 39.9%
- 2013: 40.7%
- 2015: 38.6%
- 2017: 35.6%
- 2019: 36.8%
- 2021: 27.8%
That’s a decrease of 12.1 percent, which is a surprise, in light of the legalization movement, and the data we present above about how adolescents perceive the risks and harms of using marijuana.
Tried Marijuana Before Age 13
- 2011: 8.1%
- 2013: 8.6%
- 2015: 7.5%
- 2017: 6.8%
- 2019: 5.6%
- 2021: 5.9%
That’s a decrease of 2.2 percent, which is encouraging, because evidence indicates that the earlier a person initiates marijuana use, the greater the negative long-term physical and mental health consequences.
Current Marijuana Use (Past 30 Days)
- 2011: 23.1%
- 2013: 23.4%
- 2015: 21.7%
- 2017: 19.8%
- 2019: 21.7%
- 2021: 15.8%
That’s a decrease of 7.3 percent overall, which is both surprising and encouraging. It’s surprising in light of the legalization movement, as we mention above. It’s encouraging because less frequent use is associated with fewer negative long-term physical and mental health consequences.
Ten Year Trends in Teen Marijuana Use: By Gender and Grade Level
Once they obtained the big picture, general trend results, the research team dug deeper into the data to learn more specific details. Here’s the breakdown by gender:
Current Marijuana Use (Past 30 Days) By Gender
- 2011: Male: 25.9% / Female: 20.1%
- 2013: Male: 25% / Female: 21.9%
- 2015: Male: 23.2% / Female: 20.1%
- 2017: Male: 20% / Female: 19.6%
- 2019: Male: 22.5% / Female: 20.8%
- 2021: Male: 13.6% / Female: 17.8%
In 2021, marijuana use among high school age females surpassed use among high school age males for the first time since the YRBS initiated data collection on marijuana use. This is a significant finding we can use in our ongoing work with teenage girls with various mental health disorders.
Finally, the researchers analyzed he data by grade level, with the following results:
Current Marijuana Use (Past 30 Days) By Grade Level
- 2011: 9th: 18% / 10th: 21.6% / 11th: 25.5% / 12th: 28%
- 2013: 9th: 17.7% / 10th: 23.5% / 11th: 25.5% / 12th: 27.7%
- 2015: 9th: 15.2% / 10th: 20% / 11th: 24.8% / 12th: 27.6%
- 2017: 9th: 13.1% / 10th: 18.7% / 11th: 22.6% / 12th: 25.7%
- 2019: 9th: 14.6% / 10th: 19.8% / 11th: 24.9% / 12th: 28.3%
- 2021: 9th: 9.1% / 10th: 13.3% / 11th: 18.7% / 12th: 22.4%
Again, the numbers show us a trend we didn’t expect and wouldn’t have predicted: a distinct downward trend in marijuana use among high school students during the time period of widespread legalization of marijuana. Use by 9th graders decreased by half, which is good news, given the facts on the negative consequences of early initiation. Use also declined significantly for 10th graders, which is also good news.
Although overall use by 11th and 12th graders decreased, rates are still significantly elevated, compared to young students. The research team suggests this is the result of increasing independence and increased likelihood of exposure to marijuana access through expanding social circles.
How This Research Can Help Us Improve Teen Mental Health
This information on teen marijuana use is crucial to our mental health work for several reasons. First, there’s a connection between substance misuse and mental health disorders, in general. Second, there’s a phenomenon called marijuana-induced psychosis, which is rare, but real. Finally, Dr. Volkow assigns medium confidence to the evidence connecting marijuana use with depression, anxiety, and schizophrenia.
We treat adolescents and young adults diagnosed with the mental health disorders associated with marijuana use – and we understand the connection between substance misuse and mental health. In many cases, teens turn to marijuana to manage uncomfortable, painful, or distressing emotions associated with mental health disorders. In other cases, teens may use marijuana to manage emotions associated with past/childhood trauma.
When we understand the origin of a mental health disorder, we can better help and support our patients. This new information works on us in two ways: we’re relieved that teen marijuana use is decreasing, and at the same time, we’re now aware of the fact that among female adolescents, marijuana use is increasing, which may have long-term negative effects on their overall physical and mental health.
