New Study of 11,000 Teens Links Cannabis Use to Slower Brain Development

As cannabis becomes more accepted and widely available, many families are asking an important question: what does it mean for teenagers?

A recent report highlighted by ScienceAlert summarizes one of the largest U.S. studies to date on adolescent cannabis use. Researchers tracking more than 11,000 children and teens found that young people who began using cannabis showed slower gains in memory, attention, and thinking skills compared with peers who did not use it.

Why the Teenage Years Matter

Experts note that adolescence is a critical period for brain development. During these years, the brain is still refining:

• decision-making
• impulse control
• memory systems
• attention
• emotional regulation

Because these systems are still developing, substances may affect teenagers differently than adults.

What the Study Found

The research used data from the long-running Adolescent Brain Cognitive Development (ABCD) Study, following participants from ages 9–10 into later teenage years.

Teens who used cannabis tended to show:

• slower progress in memory
• weaker gains in focus and processing speed
• reduced improvement in broader cognitive skills over time

Importantly, some users performed similarly—or even slightly better—before cannabis use began. The gap appeared after use started.

THC May Be the Key Concern

Researchers also found that exposure to THC—the psychoactive ingredient in cannabis—was more strongly linked to memory problems than CBD-only exposure in a smaller subgroup. This may matter because modern cannabis products often contain much higher THC levels than in previous decades.

What This Does Not Mean

The study found an association, not absolute proof of causation. Human behaviour is complex, and factors such as stress, family environment, mental health, and peer influences also matter.

Still, researchers adjusted for many of these variables, and the pattern remained significant enough to raise concern.

The Lydia™ Perspective

For many mothers, aunties, sisters, and women guiding younger people, this topic can feel difficult.

Cannabis is often marketed as natural, harmless, or no worse than alcohol. But “natural” does not always mean risk-free—especially for a developing brain.

This is not a call for panic or shame. It is a call for informed, compassionate conversations.

At Lydia™, we believe young people need facts, support, and guidance—not fear.

A Gentle Reminder

If a teenager in your life is using cannabis, the most effective first step is often not confrontation—but connection.

Ask questions. Stay calm. Keep communication open.

That relationship may protect them more than any lecture.

Full Citation

Cockerill, Jess. “Study of 11,000 US Teens Links Cannabis Use to Slower Brain Development.” ScienceAlert, April 22, 2026. Based on research published in Neuropsychopharmacology.