Teen Marijuana Use May Cause Schizophrenia, Study Finds

Regular marijuana use in adolescence may permanently impair brain function and cognition and may increase the risk of developing psychiatric disorders such as schizophrenia, according to a study from the University of Maryland School of Medicine. 

The research, which was released Wednesday amid numerous state-level battles over medical marijuana laws—including one here in New Jersey—is aimed at shedding light on the potential long-term effects of marijuana use during development, according to its authors.

"Adolescence is the critical period during which marijuana use can be damaging," says the study's lead author, Dr. Sylvina Mullins Raver. "We wanted to identify the biological underpinnings and determine whether there is a real, permanent health risk to marijuana use."

In the study, the scientists exposed young mice to very low doses of the active ingredient in marijuana for 20 days and then allowed them to return to their siblings and develop normally.

The adult mice exposed to small doses of marijuana ingredients in adolescence exhibited impaired cognitive abilities and impaired cognitive behavioral performance, said Raver. 

“The striking finding is that, even though the mice were exposed to very low drug doses, and only for a brief period during adolescence, their brain abnormalities persisted into adulthood,” she said.

When the scientists repeated the experiment using adult mice that had never been exposed to the drug before, the cognitive behavioral tasks of the mice remained normal. 

Scientists say the results indicated that it was only drug exposure during the critical period of adolescence that impaired cognition.

When they tried to pinpoint the underlying mechanisms of brain development

"We looked at the different regions of the brain," said one of the study's senior authors Dr. Asaf Keller, a professor of anatomy and neurobiology at UMSM. "The back of the brain develops first, and the frontal parts of the brain develop during adolescence. We found that the frontal cortex is much more affected by the drugs during adolescence. This is the area of the brain controls executive functions such as planning and impulse control. It is also the area most affected in schizophrenia."

Keller and his team believe the results have indications for humans as well. 

“Previous research has shown that children who started using marijuana before the age of 16 are at greater risk of permanent cognitive deficits, and have a significantly higher incidence of psychiatric disorders such as schizophrenia,” said Keller. “There likely is a genetic susceptibility, and then you add marijuana during adolescence and it becomes the trigger.”

Gov. Christie has been mum on whether he would sign a bill currently on his desk that would make medical marijuana more accessible to minors.

Under New Jersey’s current medical marijuana law, access is permitted to children with the consent of three medical doctors. The pending law would change that policy to require just one physician to consent.

"As for children... I'm very reluctant to go down this slope,” Christie said at a conference earlier this month. 

He said his counsel's office is currently reviewing S-2842, the bill which would lessen the three-physician restriction for children, and that he would make a decision at a later date.

"If folks can't get physicians to sign off on this, then that tells me something,” Christie said.