The Cost of Getting High Young

Most parents think they know where their teenager stands on marijuana use. Many are wrong. Today, marijuana is more available to teens than it has ever been. Legalization has spread across dozens of states. Prices have dropped. Social stigma has faded. And the products on the market are far more potent than what previous generations encountered.

The science, though, has not softened along with public opinion. Researchers are finding that marijuana use during the teen years carries real risks. Some of those risks are long-lasting. A few may be permanent. The adolescent brain is still developing well into a person’s mid-twenties. That makes it especially sensitive to outside chemicals, including THC.

In 2022, the CDC reported that 30.7 percent of U.S. high school seniors used cannabis in the past year. About 6.3 percent reported daily use. Even as some trends have shifted, experts warn that reduced stigma can lead teens to underestimate the risks. Understanding what marijuana use actually does to a young brain is the starting point for any real conversation.

A Brain That Is Still Being Built

The teenage brain is not a smaller version of an adult brain. It is a brain in the middle of major construction. Key regions are still forming. The prefrontal cortex, which handles decisions and impulse control, does not fully mature until around age 25. That window of development is also a window of vulnerability.

The National Institute on Drug Abuse has stated clearly that marijuana use during adolescence can cause long-term or permanent changes to the brain. Animal studies back this up. Rats exposed to THC during their adolescent period showed lasting problems with memory and learning. Their hippocampus, the part of the brain tied to memory, showed structural damage that persisted into adulthood.

Human brain imaging research supports these findings. Studies published in Frontiers in Psychiatry found structural changes in the hippocampus and amygdala among teen marijuana users. These changes affect memory, emotional regulation, and the reward system. Together, that is a wide range of brain functions that marijuana use can disrupt during a critical period of growth.

“Cannabis use can have permanent effects on the developing brain when use begins in adolescence, especially with regular or heavy use.” — U.S. Centers for Disease Control and Prevention

What Marijuana Use Does to IQ

One of the most discussed studies on this topic followed participants in Dunedin, New Zealand from birth to age 38. The results were striking. Teens who developed heavy marijuana use habits lost an average of 6 IQ points by mid-adulthood. Some lost up to 8 points. Adults who started heavy use later in life showed no such loss.

What made the findings especially sobering was this: quitting did not fix the damage. Those who used heavily as teens and stopped as adults did not recover the lost IQ points. The window for that harm appears to be the adolescent years specifically. This is not a general risk of marijuana use. It is a risk tied directly to when use begins.

Additional research from the Coronary Artery Risk Development in Young Adults study tracked nearly 4,000 people across 25 years. Researchers found that cumulative marijuana use was linked to lower verbal memory scores in mid-adulthood. Furthermore, a 2023 study in Frontiers in Psychiatry built specifically to isolate marijuana’s effect on teen cognition confirmed declines in working memory, processing speed, and verbal learning. The evidence, taken together, is consistent and difficult to dismiss.

Grades, Motivation, and Everyday Functioning

The effects of marijuana use do not stay inside the brain. They show up in the classroom, in grades, and in daily behavior. Research consistently links teen marijuana use to lower academic performance and reduced engagement at school.

In December 2025, Columbia University Irving Medical Center published a study in Pediatrics that examined cannabis use across thousands of adolescents. Teens who used cannabis just once or twice a month showed higher rates of depression, anxiety, and impulsive behavior compared to those who did not use at all. Near-daily users were nearly four times as likely to have poor grades. They also disengaged from school activities more often. Younger users showed even stronger associations.

The CDC reports that teens who use marijuana are more likely to drop out of high school. They are also less likely to earn a college degree. Those outcomes ripple forward into career prospects, income, and long-term stability. So the impact of marijuana use does not stop when a teen grows up. It follows them into adulthood in practical, measurable ways.

Mental Health Risks Are Real and Significant

Mental health is one of the most important areas where researchers have found strong links to teen marijuana use. A 2022 scoping review published through the National Institutes of Health found substantial evidence connecting adolescent marijuana use to worse long-term mental health outcomes. The risks were notably higher than those seen in adult users.

Psychosis is among the most serious concerns. Studies cited by NIDA link early marijuana use to a higher likelihood of developing psychosis or schizophrenia-spectrum disorders later in life. The risk rises with frequency of use and with higher THC concentrations. Genetics can also play a role. Teens with certain predispositions face an even higher risk when marijuana use begins young.

There is also a paradox worth understanding. Teens often feel fewer immediate negative effects from marijuana than adults do. That can make the drug seem safer than it is. The 2022 NIH review noted this directly: adults actually report more acute adverse effects than teens do. So the short-term experience does not accurately signal the long-term risk. For a teenager trying marijuana use for the first time, that gap between immediate feeling and actual harm is a genuine danger.

Who Is Using and Why It Matters

Marijuana use among teens does not look the same across all groups. Recent research points to meaningful shifts in who is using, and those shifts carry different risks depending on the individual.

A 2024 study published in Pediatric Reports tracked Youth Risk Behavior Survey data from 2011 to 2021. One of the most notable findings was that by 2021, girls had surpassed boys in reported marijuana use. That is a significant reversal. Researchers believe evolving social dynamics and more integrated peer groups have contributed to the shift. But the implications are serious. NIH research has documented what is called a telescoping effect in women. That means female users tend to progress from first use to cannabis use disorder more rapidly than male users do.

There are also racial and ethnic disparities in who uses marijuana and who has access to prevention and treatment. These gaps matter because the harms of marijuana use are not distributed equally. Effective public health responses need to account for these differences. A one-size-fits-all approach will not reach the teens who need support most.

The Biggest Study on Teen Brains Ever Conducted

In 2015, the National Institutes of Health launched the Adolescent Brain Cognitive Development Study, known as the ABCD Study. It enrolled more than 11,000 children at ages 9 and 10. Researchers are following them through adolescence and into adulthood. It is the largest long-term study of brain development and child health ever conducted in the United States.

The ABCD Study tracks participants using MRI imaging, cognitive testing, genetic analysis, and detailed behavioral surveys. NIDA leads the cannabis-specific research within the study. Researchers at UC San Diego alone are tracking 700 participants from the region with the full battery of tools. The goal is to build a clear, longitudinal picture of how marijuana use and other factors shape the developing brain over time.

The study is still generating data as participants age into their twenties. Early findings support what existing research has shown. Scientists expect the full dataset to settle some of the remaining questions about causation. Cross-sectional studies can show correlations. The ABCD Study is built to show what actually causes what. The results will shape how schools, doctors, and policymakers talk about teen marijuana use for decades to come.

What Parents and Communities Can Do

The research sends a clear message: delay matters. The later marijuana use begins, the less damage accumulates. A 2022 NIH scoping review put it directly. Cannabis use should be delayed as late as possible into adulthood to lower the risk of negative outcomes. That is not a moral argument. It is a neurological one.

Columbia University researchers recommend that parents have honest, low-pressure conversations with teens about marijuana use early and often. The framing matters. Leading with punishment or shame tends to shut conversations down. Leading with facts tends to keep them open. Parents should also know what to watch for. Declining grades, mood changes, withdrawal from hobbies, and new peer groups can all signal that something has shifted.

Schools and policymakers face a harder challenge. Legalization has softened public perception of risk just as the science on teen marijuana use has become more alarming. Effective messaging needs to be honest without being alarmist. It needs to be specific enough to be credible. And it needs to reach teens where they actually are, online, in social feeds, and in honest conversations rather than in outdated classroom scare tactics.

The good news is that awareness works. Studies show that when teens understand the specific risks tied to marijuana use at their age, many adjust their behavior. The science is there. The question is whether it reaches young people in a way they can actually use.

Key takeaways for families:

• Teen marijuana use is linked to lasting IQ loss, memory deficits, and lower educational attainment.
• Mental health risks are significantly higher for adolescent users than for adult users.
• Girls now match or exceed boys in reported marijuana use and progress to dependency faster.
• The single most protective factor is delay. Later is always better than earlier.
• Honest, fact-based conversations with teens are more effective than fear-based messaging.

Article at a Glance

Sources

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• National Institute on Drug Abuse. (2025). The Adolescent Brain and Substance Use. nida.nih.gov
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• Variations of cannabis-related adverse mental health outcomes: A scoping review. (2022). PMC9590692. NIH.
• Columbia University Irving Medical Center. (December 2025). Teen cannabis use and emotional health. Pediatrics.
• Trends in Marijuana Use among Adolescents in the United States. (2024). Pediatric Reports, 16(4).
• Cannabis use in adolescence and effects on brain structure: A scoping review. (2025). Frontiers in Psychiatry.
• American Psychological Association. (2023). How does marijuana affect the brain? APA Monitor.