A new study showing a relationship between marijuana use and brain abnormalities is facing scrutiny from some Gainesville experts and residents.
The study, conducted by Hans C. Breiter, included 20 users between the ages 18 to 25 and 20 nonusers who were matched by sex, age and other traits. The recreational users claimed to smoke an average of four days a week.
Jodi Gilman, co-author of the study and a neuroscientist at Massachusetts General Hospital, said the results showed a range of abnormalities in the brain of marijuana users.
“We saw greater gray matter density in marijuana (users) than in control participants in the nucleus accumbens and the amygdala,” she wrote in an email. “We also saw shape abnormalities in the left nucleus accumbens and right amygdala.”
Gilman said this is the first study to show abnormalities in young adult moderate users. She said the abnormalities were dose-dependent, which means the differences were more pronounced in those who reported using more marijuana.
But Julia Rae Varnes, a specialist at GatorWell Health Promotion Services, said the study only shows a relationship between marijuana use and brain abnormalities, but it doesn’t show a causal relationship.
“The study was cross-sectional and used participants who were self-selected marijuana users. That means we don’t know which came first — the brain abnormalities or the marijuana use,” Varnes wrote in an email.
However, Varnes said she thinks marijuana use can have downsides.
“Many drugs, including legal drugs, have the potential to negatively affect the brain,” she said. “Any drug has some potential for negative effects period.”
Daniel Gomez, a 19-year-old business management sophomore at Santa Fe College, said he doesn’t think smoking marijuana moderately would have a negative effect.
“I personally think marijuana could negatively affect you if you smoke excessively,” he said. “If you smoke like three or four times a week, and you’re still being productive, I don’t see a problem with that.”
Gilman said the next thing to study is the relationship between these structural abnormalities in the brain and functional outcomes.
“I also think it’s important to assess how structure effects relate to the addictive properties of cannabis for each individual,” she said.
[A version of this story ran on page 4 on 4/18/2014 under the headline "Locals question study about marijuana effects on brain"]
