Scientists at the University of California, San Diego studied more than 11,000 kids to see how using cannabis affects the brain. They found that teens who try cannabis may grow slower in memory, attention, language and thinking speed.
How the Study Was Done
The researchers followed 11,036 children from age 9‑10 until they were 16‑17 years old. They checked the kids’ school‑type skills and also tested their bodies (hair, urine, saliva) to know if they had used cannabis.
Kids who used cannabis showed less improvement over time in several mental areas. Some of them started out as well as other kids, but once they began using cannabis their learning slowed while non‑users kept getting better.
THC Appears to Harm Memory
When the team looked at the chemicals in the plant, they saw that teens with signs of THC – the main intoxicating part of cannabis – lost more memory ability than kids who did not use cannabis.
Teenagers with signs of CBD did not show the same memory drop, but the group was small.
Small Changes Can Matter
Even tiny differences in memory or attention can matter a lot for school work and daily life because the teenage brain grows fast.
The study does not prove that cannabis is the only cause. Things like family situation, mood, other drug use, or personal traits could also play a role. The scientists tried to control for many of these factors.
What Comes Next
The researchers will keep watching the participants as they become adults. Future results may show whether the age of first use or how often cannabis is used changes the brain even more.
“Waiting to use cannabis helps the brain develop healthily,” one researcher said. “As cannabis becomes easier to get, families and teens should know how it might affect growing brains.”