Home > Cannabis & Mental Health > Cannabis & the Teenage Brain

Cannabis and the Teenage Brain: What Parents Need to Know

The Science Behind Why Cannabis Is Different Before Age 25
By Dr. Ryan S. Sultan, Assistant Professor of Clinical Psychiatry
Columbia University Irving Medical Center
NIH NIDA-Funded Cannabis Researcher | Published in Pediatrics & JAMA Network Open

Contents:
Why Teens Are Different | The Endocannabinoid System | What THC Does to the Developing Brain | The IQ Question | What My Research Shows | Psychosis Risk | Today's Potency Problem | Signs Your Teen May Be Using | What Parents Can Do | FAQ

Why the Teenage Brain Is Different

The brain continues developing until approximately age 25. This is not a rough estimate — it is one of the most well-established findings in developmental neuroscience. Between adolescence and the mid-twenties, the brain is doing three critical things:

• Pruning unused connections — eliminating neural pathways that aren't needed to make the remaining ones more efficient
• Myelination — insulating nerve fibers with white matter to speed up communication between brain regions
• Building the prefrontal cortex — the region responsible for judgment, impulse control, planning, and decision-making. This is the last region to finish

The connections between the emotional centers of the brain (the amygdala, the reward system) and this "command center" (the prefrontal cortex) are still being installed throughout this period. The reward system is also being calibrated, which is why teenagers are naturally drawn to novelty and risk.

This is why cannabis is fundamentally different for a 16-year-old than for a 30-year-old. In adults, cannabis acts on a finished brain. In teenagers, it interferes with the construction process itself.

The Endocannabinoid System: Your Brain's Construction Foreman

Here is the part most people don't know: the brain has its own cannabinoid system, called the endocannabinoid system (ECS). This system produces natural cannabinoids (anandamide and 2-AG) that bind to CB1 receptors throughout the brain.

This system does not exist to get people high. It exists to guide brain development.

The ECS regulates:

• Neural pruning — deciding which connections to keep and which to eliminate
• Neuroplasticity — the brain's ability to reorganize and adapt
• Stress response calibration
• Reward system tuning
• Memory formation and consolidation

CB1 receptors are among the most abundant receptors in the brain. They are concentrated in exactly the regions undergoing the most active development during adolescence: the hippocampus (memory), prefrontal cortex (judgment), and amygdala (emotion).

What THC Does to the Developing Brain

When a young person uses cannabis, THC floods into the brain and overstimulates CB1 receptors at levels far beyond what the body's own cannabinoids would produce. The brain responds by shutting down receptors — a process called downregulation — leaving fewer available for the normal developmental work they are supposed to be doing.

The consequences are measurable:

The IQ Question: 8 Points That Don't Come Back

The most striking evidence comes from the Dunedin Multidisciplinary Health and Development Study — a landmark longitudinal study that followed over 1,000 people from birth to age 38 (Meier et al., Proceedings of the National Academy of Sciences, 2012).

Eight IQ points is the difference between being at the 50th percentile and the 29th percentile — between average and below average. This is not a subtle effect.

Why can't you get those points back? Because the drug was present during construction. The pruning that happened too early cannot be reversed. The connections that were never properly formed do not appear later. In adults, the brain largely recovers after stopping cannabis use. In adolescents, it does not, because the blueprint was altered while the building was still going up.

What My Research Shows: 162,532 Adolescents

My NIH-funded research has produced two large-scale studies examining cannabis effects across the full spectrum of adolescent use:

Sultan et al., Pediatrics 2026 (N = 162,532)

This study examined a nationally representative sample of U.S. adolescents and found dose-dependent harms across every domain measured — academic, emotional, and behavioral:

The critical finding: there was no "safe" frequency of use. Even monthly cannabis use was associated with measurably worse outcomes compared to non-use. The more frequently adolescents used, the worse they did — a classic dose-response relationship that strengthens the case for causation.

Sultan et al., JAMA Network Open 2023 (N = 68,263)

This study specifically examined adolescents who used cannabis without meeting criteria for addiction (nondisordered cannabis use) — the "casual" users many people assume are fine:

Sultan RS, Zhang AW, Olfson M, Kwizera MH, Levin FR. JAMA Network Open. 2023;6(5):e2311294.

The bottom line: you don't have to be addicted to be harmed. The 10.2% of U.S. adolescents using cannabis "casually" are experiencing real, measurable consequences — nearly double the depression rate and more than double the rate of suicidal thoughts.

The Psychosis Risk

One of the most alarming findings in cannabis research involves psychotic disorders. The risk is highest for adolescents because their dopamine system and prefrontal cortex are still maturing.

Key data points:

• Young-Wolff et al. (2026, JAMA Health Forum, N = 463,396): Cannabis use disorder associated with 2.19x higher hazard of developing a psychotic disorder. The effect was strongest among those aged 13-15
• Di Forti et al. (2019, Lancet Psychiatry): Daily use of high-potency cannabis associated with 5x higher odds of first-episode psychosis
• Approximately 50% of those who experience cannabis-induced psychosis go on to develop a permanent psychotic condition — the highest conversion rate of any substance-induced psychosis
• Males appear to be at particularly elevated risk, with cannabis use roughly doubling the odds of developing a psychotic disorder by young adulthood

Critically, the Young-Wolff study found that risk was age-dependent: the depression hazard ratio was 1.78 at ages 13-15, declining to 1.35 at ages 16-17, 1.21 at ages 18-20, and not significant by ages 21-25. The same age-gradient appeared across all psychiatric outcomes. The younger the brain, the greater the vulnerability.

For a comprehensive analysis, see our full article: Cannabis and Psychosis: What the Research Shows

Today's Potency Problem

Most of what parents "know" about marijuana comes from a different era. The cannabis available today is pharmacologically a different drug:

This matters for two reasons:

1. Higher THC = more endocannabinoid disruption. The developing brain's CB1 receptors are overwhelmed at these concentrations
2. CBD has been bred out. CBD (cannabidiol) may have neuroprotective properties that partially offset THC's harms. Modern cannabis has virtually eliminated this buffer

A teenager using a vape pen with 85% THC oil is not having the same experience as someone who smoked 4% THC flower in 1993. Parents who say "I smoked pot and I turned out fine" are comparing a glass of beer to a bottle of vodka.

Signs Your Teen May Be Using Cannabis

Behavioral changes:

• Declining grades or loss of interest in school
• New friend group, especially one that is secretive
• Loss of interest in activities they used to enjoy
• Increased secrecy about phone, social media, whereabouts
• Bloodshot or glassy eyes, frequent use of eye drops
• Unusual smells on clothing (or excessive cologne/air freshener to mask it)
• Increased appetite (munchies), especially at unusual times
• New paraphernalia: vape pens, rolling papers, grinders, small glass pipes

Cognitive/emotional changes:

• Memory problems — forgetting conversations, appointments, assignments
• Slower processing speed — takes longer to respond, seems "foggy"
• Decreased motivation — the "amotivational syndrome"
• Mood instability — more irritable, anxious, or flat
• Sleep pattern changes — staying up later, harder to wake

Many of these overlap with normal adolescent development, depression, or ADHD. Do not assume — have a conversation. If you suspect use, screening by a healthcare provider is the appropriate next step.

What Parents Can Do

1. Start the conversation early — and keep it science-based

Teenagers are resistant to authority-based messaging ("because I said so") but responsive to evidence. Explain why the brain is vulnerable before age 25. The endocannabinoid system explanation resonates with curious teens because it gives them a concrete mechanism rather than a vague warning.

2. Focus on delay, not just abstinence

The evidence is clear that risk decreases substantially with each year of delayed onset. If a teen is already using, any reduction in frequency and quantity is meaningful. Moving from daily use to weekend use reduces exposure significantly. Working toward reduction rather than demanding immediate abstinence is often more realistic and more effective.

3. Know what you're up against

Today's products — especially vape pens — are nearly odorless, easily concealable, and deliver THC at concentrations your generation never encountered. Edibles look like regular candy. Be aware of these delivery methods.

4. Screen for co-occurring conditions

Teens with untreated ADHD, anxiety, depression, or trauma are significantly more likely to self-medicate with cannabis. Treating the underlying condition reduces the drive to use. See our article on Cannabis and ADHD for more on this overlap.

5. Seek professional help if needed

If your teen is using regularly (weekly or more), or if use is causing academic, social, or emotional problems, evaluation by a psychiatrist experienced in adolescent substance use is appropriate. Evidence-based treatments include motivational interviewing, cognitive behavioral therapy, and family-based approaches.

Frequently Asked Questions

Does marijuana kill brain cells?

Not in the traditional sense. Cannabis does not cause neuronal death the way a severe traumatic brain injury does. What it does is arguably worse for a developing brain: it disrupts the construction process. The hippocampus physically shrinks, white matter integrity is compromised, and the prefrontal cortex must recruit extra neurons to perform basic tasks. In teenagers, these structural changes may be permanent.

Is one time going to damage my teen's brain?

Single or very occasional use is unlikely to cause lasting structural changes. The research on IQ loss and brain damage involves regular, persistent use — typically weekly or more for extended periods. However, even single episodes can trigger acute anxiety, panic attacks, or in vulnerable individuals, psychotic symptoms. There is no established "safe" dose.

My teen only uses edibles — is that safer?

No. Edibles deliver the same THC to the brain through a different route. In some ways, they carry additional risks: delayed onset (30-90 minutes) means teens often consume more while waiting to "feel it," and the effects last much longer (6-8 hours vs. 2-3 hours from inhalation). The brain damage is from THC exposure, regardless of delivery method.

Is CBD safe for teenagers?

Pure CBD does not appear to carry the same risks as THC. CBD does not activate CB1 receptors in the same way and may even have neuroprotective properties. However, most CBD products are unregulated and may contain THC. Third-party tested, THC-free CBD is a different conversation from cannabis flower or THC products, but evidence for its use in healthy adolescents is limited.

My teen says cannabis helps their anxiety. What should I say?

Acknowledge the short-term experience while explaining the long-term reality. THC can reduce anxiety in the moment at low doses — that is real. But research consistently shows cannabis worsens anxiety over time (see our Cannabis and Anxiety article). More importantly, using cannabis for anxiety during adolescence means the brain's stress-response system never learns to regulate itself. A psychiatrist can identify more effective, evidence-based treatments for adolescent anxiety.

What about states where marijuana is legal?

Legal does not mean safe — especially for developing brains. Alcohol is legal for adults over 21, but no physician would recommend a 16-year-old drink regularly. Cannabis legalization is an adult policy decision. The neuroscience of adolescent brain development does not change with legislation.