Teen Marijuana Use: Compared to Adults, What’s the Risk of Addiction and Mental Health Disorders?

Twenty years ago, recreational cannabis products were illegal in almost every state in the country. Twenty-one states allowed the medical use of cannabis, and in 14 states, possession of small amounts of cannabis was decriminalized.

However, marijuana was completely illegal for medical and recreational use in most states, and cannabis use among teenagers was at its lowest point since 1979.

Now, in the year 2022, things have changed.

Recreational cannabis is legal for people over age 21 in 19 states and Washington, D.C. Medical marijuana is legal in 38 states and Washington, D.C.

The movement toward the legalization of recreational cannabis raised questions and concerns among adults about the impact it might have on teens. Would teens increase their marijuana use? Would that have a negative impact on their mental health, their academic achievement, and their overall life functioning?

We wrote an in-depth article that explored those questions. It’s published on our blog:

Teen Marijuana Use in the New Era of Legalization

We encourage you to read that article. It discusses trends in marijuana use, trends in legalization, and reviews the strength of evidence that associates adolescent cannabis use with various negative behavioral and psychological consequences.

Here’s a quick recap of that piece.

Marijuana use trends, 1979-2016:

  • Declined between 1979-1992
  • Increased between 1992-2001
  • Decreased between 2001-2006
  • Increased between 2006-2016

Marijuana laws:

  • 1970s: Decriminalized in 14 states
  • 1990s: Medical marijuana legalized in 21 states
  • 2012-2022: Recreational marijuana use in legalized in California and Washington in 2012, other states follow suit

Strength of evidence for negative consequence of marijuana use:

  • Risk of addiction: strong
  • Abnormal brain development: medium
  • Association with schizophrenia: medium
  • Association with depression or anxiety: medium

Based on that data, it appears the increase in availability of marijuana poses a strong risk of addiction and a moderate risk of developing mental health disorders among teens.

That’s what a study published recently got our attention: it examined the risk of addiction and risk of mental health disorders in adolescent marijuana users compared to adult marijuana users.

Let’s take a look at what they found.

Does Marijuana Use Lead to Addiction and Mental Health Disorders?

The researchers who published the paper “The Cannteen Study: Cannabis Use Disorder, Depression, Anxiety, and Psychotic-Like Symptoms in Adolescent and Adult Cannabis Users and Age-Matched Controls” hypothesized three things about the marijuana use among adolescents and adults:

  1. Adolescents are more likely than adults to develop marijuana addiction, called cannabis use disorder (CUD).
  2. Cannabis users are more likely to show higher levels of depression, anxiety, and psychosis, compared to non-users.
  3. Adolescent cannabis users will be more likely than adult cannabis users to develop depression, anxiety, and psychosis.

To test their hypotheses, researchers recruited a total of 274 participants, including:

  • 76 adolescent cannabis users, age 16 and 17
    • 63 control subjects, non-cannabis users, age 16 and 17
  • 71 adult cannabis users, ages 26-29
    • 64 control subjects, non-cannabis users, ages 26-29

To determine the effect of cannabis use on rates of CUD, depression, anxiety, and psychosis, researchers administered the following standard psychiatric assessments:

  • Cannabis use disorder: Diagnostic and Statistical Manual (DSM-5) criteria for Cannabis Use Disorder (CUD)
  • Depression: Beck Depression Inventory
  • Anxiety: Beck Anxiety Inventory
  • Psychosis: Psychotomimetic States Inventory-adapted.

Let’s take a look at what they found.

Cannabis Use, Addiction, and Mental Health: Teens and Adults

1. Cannabis Use Disorder

    • Adolescent cannabis users were 3.5 times – or 250% – more likely to develop CUD than adult cannabis users

2. Depression

    • There was no observable difference in rates of depression among adolescent cannabis users compared to adult cannabis users

3. Anxiety

    • There was no observable difference in rates of anxiety among adolescent cannabis users compared to adult cannabis users

4. Psychosis

    • All cannabis users showed higher rates of psychotic-like symptoms than non-cannabis users
    • Adolescent cannabis users showed higher rates of psychotic-like symptoms than adult cannabis users

5. Severity of CUD

    • Initial exploratory analysis indicated that in both age groups, cannabis users with severe CUD showed higher rates of depression and anxiety than cannabis users without severe CUD

We’ll discuss these results below.

What Does This Study Mean for Parents and Teens?

First, it’s important for parents and teens to remember the fact that although recreational cannabis use is legal in almost half the country, the legal age for purchase and use is 21.

That means all teens who use marijuana – in any amount, at any time, in any context – are breaking the law.

We’ll just leave that there without commentary.

Second, we’ll point out that this study confirms the previous research we reported in the in-depth article we link to above: teens who use cannabis are at higher risk than adults of developing cannabis use disorder (CUD), a.k.a. cannabis addiction.

Third, we’ll note that addiction of any kind – to marijuana, to alcohol, to opioids – can cause significant disruption and lead to problems in school, problems in relationships, and problems engaging fully in the typical functions of daily life.

The study we discussed today did not identify an increased risk of mental health disorders for adolescent cannabis users compared to adult cannabis users. That’s a significant finding. It enhances our overall understanding of the psychological consequence of cannabis use. The study did, however, identify increased rates of symptoms of depression and anxiety in people with severe CUD compared to people without severe CUD.

That’s another significant finding, and connects the dots with regards to risk of cannabis use among teens, in relation to mental health disorders. Here’s what we mean:

  • Adolescent cannabis use increases risk of CUD
  • Presence of CUD increases risk of severe CUD
  • Severe CUD is associated with increased symptoms of depression and anxiety

When we look at this data with this broad perspective, we understand the risk adolescent cannabis use poses: the impact may not be immediate, but in the long run, use of cannabis by adolescents increases risk of addiction, which, in turn, increase risk of additional psychological issues. Among those risks are the development of severe CUD, which is associated with increased risk of mental health disorders.

Therefore, this research confirms and validates what most parents already know:

Cannabis may be legal for adults, but for teens, it’s not necessarily safe: this study shows cannabis use during adolescence increases risk of addiction, which creates a new set of problems with serious long-term consequences.