Study Suggests 'Pothead' Stereotype Might Be Real
Teens who smoked or had smoked in the past had shrunken structures in areas linked to memory
The study confirms earlier findings that showed memory loss in young marijuana users, said Dr. Scott Krakower, assistant unit chief of psychiatry at Zucker Hillside Hospital in Glen Oaks, N.Y.
But Krakower said more work needs to be done before it's proven that marijuana actually causes changes in the brain. "Future research needs to be done to verify the implications of marijuana use on the ... structure of the brain," he said. "It needs to be studied in a group of people over a period of time."
Dr. Mitch Earleywine, a professor of psychology and director of clinical training at the State University of New York at Albany, agreed that the results need to be replicated.
"Brain structural studies often look at every single spot and then capitalize on the ones that are significant by chance," said Earleywine, author of the book Understanding Marijuana. "We've had no structural deficits in folks who started using as adults, so researchers went to adolescents."
Earleywine said marijuana users have been shown to perform more poorly on memory tests due to the stress they endure taking such tests.
"If you can imagine going into a lab to take a memory test because you've been selected for your cannabis use, then a bevy of white-coated folks who might think that cannabis use impairs memory start giving you memory tests, you might not do so well," he said. "We've found this for males in my lab."
The Northwestern study also noted that these changes in brain structure are similar to those associated with having schizophrenia.
"If someone has a family history of schizophrenia, they are increasing their risk of developing schizophrenia if they abuse marijuana," Smith said.
But Krakower said that assertion might be a stretch.
"I thought that was a little bit of a jump," he said. "We know people with schizophrenia use marijuana. It's going to be very hard to say that someone has schizophrenia because they used marijuana. That's going to be hard to prove."
The Northwestern research is supported by grants from the U.S. National Institutes of Health.