U.S.: Marijuana Use Changes The Brain, New Study Says
By Steve Elliott
Young adults who smoke marijuana occasionally show changes in two key areas of their brains related to emotion, motivation and decision making, with the degree of changes related to the amount of cannabis used per week, according to a new study by researchers in Boston. Other scientists quickly pointed out that the research was partially sponsored by the federal agency charged with keeping marijuana illegal.
The study is believed to be the first which indicates such changes in the the brains of young, casual marijuana users, reports Kay Lazar at The Boston Globe.
The scientists did not study whether the brain changes were related to any declines in brain function. Any speculation by the scientists themselves, therefore, or especially by journalists who sensationalize the findings, about declines in cognition or functionality is therefore completely unsupported by any evidence.
But the scientists, unfortunately including lead author Jodi Gilman, did exactly that.
"This is when you are making major decisions in your life, when you are choosing a major, starting a career, making long-lasting friendships and relationships," said Gilman, sounding exactly as if she was funded by the White House Office of National Drug Control Policy (ONDCP), which only funds studies which look for negative effects of cannabis. (The study was, indeed, partially funded by the ONDCP.)
Forty young adults aged 18 to 25 were selected for the study from the Boston area. Scans measured the volume, shape, and density of two regions of the brain -- the nucleus accumbens and the amygdala. This is considered an extremely small "sample size" by scientific standards.
Half of the group said they used cannabis at least once a week, and the other 20 said they had not used it for the past year, and reported using it fewer than five times in their life. Among the group who did use marijuana, the median use was about five joints per week.
According to MRI scans, the nucleus accumbens was larger in marijuana users, compared to non-users, and the degree of its alteration was directly related to how many joints the person smoked. The nucleus accumbens is involved with decision making. The researchers also reported what they called "structural changes" in the amygdala.
Rather than interpret these findings positively as "marijuana grows new brain cells" (which previous studies have shown is the case), Gilman -- a psychology instructor at Harvard Medical School and brain scientist at Massachusetts General Hospital -- chose to speculate that the brain is forming new connecteions that "encourage further drug use," in what, without any evidence, she claimed could be "a sort of drug learning process."
Gilman claimed that results from rats in lab tests -- which also showed their brains had formed new connections as a result of marijuana -- also indicated an "unnatural level of reward and stimulation from marijuana," an almost laughably Puritanical spin on what would otherwise have been interesting scientific findings.
Other scientists who weren't involved in the study say its small sample size makes it unwise to apply to the general population.
In an inadvertent illustration of the great contrast between marijuana's capacity to grow new brain cells and forge new connections between existing brain cells, and that of cocaine to destroy them, Dr. Hans Breiter, a co-author of the Mass General study, found in one of his earlier studies that the amygdala region of the brain shrinks with cocaine use -- while the new study suggests it increases with marijuana use.
Gregory Gerdeman, a biologist and neuropharmacologist at Eckerd College in St. Petersburg, Florida, said he worries about cannabis research funded by federal agencies, like the ONDCP, which has as its mission limiting drug use, reports Karen Weintrab at USA Today, who did the best job of any mainstream reporter of covering this story.. The research was supported by grants from the ONDCP, the National Institutes of Health (NIH) and Northwestern Medicine's Warren Wright Adolescent Center.
"If you're getting money from the Drug Czar's office, that money's not going to continue if you don't end up publishing something that at least supports the general story of the danger of drug abuse," Dr. Gerdeman said.
"If it were my child, even with this study, I'm more comfortable with young people having a casual marijuana habit than drinking regularly," he added.