Cannabis and Teen Mental Health: What Our Pediatrics 2026 Study Found

Why We Did This Study

Most of the existing research on cannabis and adolescents has focused on heavy users -- daily or near-daily consumers. That makes sense from a clinical standpoint, because those are the patients who tend to show up in our offices. But it left a significant gap: what about the kids who use cannabis occasionally? The ones who smoke at a party once a month, or hit a vape pen a few times during the semester?

As a child and adolescent psychiatrist at Columbia, I see these patients regularly. Parents bring in a teenager whose grades have slipped, whose mood has changed, who seems disengaged. When I ask about substance use, the answer is often some version of: "He only smokes a little. It's not a big deal." And until this study, the honest answer was that we did not have strong population-level data to say definitively whether that occasional use mattered.

Our team set out to answer that question. We wanted to know: is there a safe level of cannabis use for adolescents? And if not, how does the frequency of use relate to the severity of problems?

What We Measured

We analyzed data from the 2018 to 2022 Monitoring the Future surveys, which are annual, nationally representative surveys of public and private high school students across the United States. Our sample included more than 160,000 eighth, tenth, and twelfth graders.

We stratified cannabis use into five groups based on monthly frequency:

• Lifetime nonusers -- never tried cannabis
• Noncurrent users -- had tried cannabis but zero occasions of use in the past month
• Monthly users -- one or two occasions per month
• Weekly users -- three to nine occasions per month
• Near-daily users -- ten or more occasions per month

Over a quarter of respondents reported any cannabis use. About 18% were noncurrent or monthly users, 3.6% were weekly users, and 4.6% were near-daily users.

We then examined a range of psychosocial outcomes: academic performance, school attendance, emotional distress, anxiety, self-esteem, impulsivity, aggression, and future orientation.

What We Found

The findings were stark, and they challenged the assumption that occasional cannabis use in teenagers is benign.

Even Monthly Use Matters

Adolescents who used cannabis just once or twice a month were approximately 1.5 to 2 times as likely to experience a poorer emotional state -- including anxiety, low self-esteem, existential distress, and anhedonia -- compared with nonusers. They were also 2 to 3 times more likely to exhibit high impulsivity and aggression.

This is the finding that surprised people outside the field. Not daily users. Not heavy users. Kids using once or twice a month were already showing measurable differences.

The Dose-Response Pattern

The relationship between cannabis use and poor outcomes followed a clear dose-response gradient. More frequent use was associated with worse outcomes across every domain we measured. Near-daily users were almost four times as likely to receive poor grades and miss school compared to nonusers.

Younger Teens Hit Hardest

All of these associations were even stronger among adolescents under age 16. This aligns with what we know about neurodevelopment: the prefrontal cortex -- the brain region responsible for decision-making, impulse control, and planning -- is still under active construction during adolescence. Cannabis disrupts that construction.

As my colleague Tim Becker, a child and adolescent psychiatrist at NewYork-Presbyterian Westchester Behavioral Health and co-author on the study, put it: "A teenager's brain is still developing the circuits for learning, self-control, and emotional regulation. Using cannabis, even casually, during these critical growth periods interferes with those processes and can derail normal development."

The THC Potency Factor

One thing that makes these findings particularly concerning is the dramatic change in cannabis potency over the past three decades. In 1995, the average THC content of cannabis was about 4%. Today, cannabis flower commonly contains 15-25% THC, and concentrates can exceed 80-90% THC.

This is a fundamentally different product than what was available a generation ago. When a parent says "I smoked weed in college and I turned out fine," they are not talking about the same substance their teenager is using. The cannabis available today delivers THC at concentrations that are 4 to 6 times higher than what was on the market in the 1990s.

Research has shown that daily use of high-potency cannabis products is associated with approximately a 4-fold increase in the risk of psychosis. That risk is not theoretical -- I see cannabis-induced psychotic episodes in my clinical practice at Columbia with troubling regularity.

The potency issue also makes dose comparisons across eras misleading. A teenager who smokes a joint once a week in 2026 may be absorbing more THC than a daily user in 1995. Our study did not measure potency directly, which means the true risk associated with current use patterns may be even greater than what we reported.

What This Means for Parents

I talk to parents about these findings regularly, and I want to be direct about what I tell them:

There is no clearly safe level of cannabis use for adolescents.

That does not mean every teenager who tries cannabis will develop problems. Many will not. But the data show that even occasional use is associated with measurable harm -- and the developing brain is not equipped to handle THC the way an adult brain can.

Here is what I recommend parents watch for:

• Declining grades -- particularly a sudden drop, not a gradual slide
• Mood changes -- increased irritability, withdrawal, loss of interest in activities they used to enjoy
• Sleep disruption -- staying up later, difficulty waking, changes in sleep patterns
• Social shifts -- new friend group, secrecy, pulling away from family
• Loss of motivation -- giving up on hobbies, sports, future planning

Any one of these could have multiple explanations. But cannabis should be on the differential, especially in a teenager who has access to it -- and in most American high schools, access is not difficult.

What This Means for Clinicians

The clinical implication of our study is straightforward: clinicians should have a low threshold for screening for cannabis use when adolescent patients present with declining academic performance, mood disturbance, anhedonia, or disengagement from previously valued activities -- even in the absence of reported frequent use.

We tend to focus our substance use screening on the heavy users, the ones who are already in crisis. This study suggests we need to cast a wider net. The teenager who uses cannabis a couple of times a month and is not in acute distress may still be on a trajectory toward worsening outcomes.

Prevention and early intervention strategies should reinforce prosocial engagement and nonsubstance-related coping, with particular attention to patients under 16. The conversation should not be "don't use drugs" -- it should be specific, evidence-based, and grounded in what the data actually show.

Our Team

This study was a collaborative effort. Our co-authors included Alexander W. Zhang, Timothy D. Becker, Pojanard Sethaputra, Keith M. Simon, Yolanda Huang, Frances Levin, Sharon Levy, and Mark Olfson. The study was led out of the Mental Health Informatics Lab at Columbia University and NewYork-Presbyterian.

I want to note that this work builds on a broader research program. Our team has also examined cannabis and psychosis risk, the effects of cannabis on the developing teenage brain, and the landscape of cannabis safety and regulation in New York City. Each piece contributes to a clearer picture of how cannabis affects young people -- and what we can do about it.

The Bigger Picture

Cannabis legalization is expanding across the United States. I do not take a position for or against legalization as a policy matter -- that is a decision for legislators and voters. But as a researcher and clinician, I do take a position on this: legalization for adults does not mean cannabis is safe for adolescents.

The parallel to alcohol is instructive. Alcohol is legal for adults. We have decades of data showing it is harmful for adolescents. We have age restrictions, public health campaigns, and clinical screening tools designed to protect young people. We need the same infrastructure for cannabis -- and we need it now, because legalization has outpaced our ability to protect kids.

Our Pediatrics study is one piece of that effort. The data are clear: even low-frequency cannabis use in adolescents is associated with real harm. The conversation about teen cannabis use needs to catch up with the evidence.

Further Reading

• Cannabis Safety and Mental Health Hub
• Cannabis and Psychosis: What the Evidence Shows
• Cannabis and the Teenage Brain
• Why I Study Cannabis and Youth Mental Health
• Schedule a Consultation