Skip to content

Brain & Nervous System Health Center

Early Marijuana Use Leads to Later Brain Problems

Adults Who Started Smoking Marijuana Before Age 16 Performed Worse on Tests Than People Who Started Smoking Later
Font Size
A
A
A

Test Results

The healthy comparison group performed better on several measures, compared to the marijuana smokers, and the early-onset smokers did worse than the late-onset smokers. The early-onset smokers ''kept not getting it," Gruber says. Despite being told their sorting was wrong after the rules change, the early-onset users kept making repeated errors. The early users also had more problems maintaining a set of rules.

For one category, for instance, early-onset smokers made 14.2 mistakes, compared to 6.4 by the late-onset smokers.

How might these cognitive problems translate to everyday life? Gruber says the early-onset smokers may have trouble with abstract thinking, for instance, or may say something socially inappropriate.

Early Marijuana Use: Perspective

The new research adds to previous studies finding other harmful brain effects, says Frances Jensen, MD, a professor of neurology at Harvard Medical School who moderated the news conference detailing Gruber's findings.

She speculates that the marijuana exposure ''is somehow modifying the way that part of the brain [the prefrontal cortex, involved in executive function tasks] is developing," she tells WebMD. "That area is one of the last parts of the brain to develop fully, she says, so the teen brain is especially vulnerable.

''Currently, it looks irreversible," she says of the damage incurred by early-onset smoking of marijuana.

This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.

1 | 2

Today on WebMD

nerve damage
Learn how this disease affects the nervous system.
senior woman with lost expression
Know the early warning signs.
 
Close up of eye
12 culprits that affect your ability to focus.
medical marijuana plant
What is it used for?
 
senior man
Article
brain research briefing
Article
 
Syringe
Article
Vaccine and needle
VIDEO
 
mans hands on laptop keyboard
Article
brain illustration stroke
Slideshow
 
most common stroke symptoms
Article
Parkinsons Disease Medications
Article