Casual pot use causes brain abnormalities in young: study

Daily News Article   —   Posted on April 17, 2014

(by Alex Dobuzinskis, Reuters) – Young, casual marijuana smokers experience potentially harmful changes to their brains, with the drug altering regions of the mind related to motivation and emotion, researchers have found.

The study, which was published Wednesday in the Journal of Neuroscience, differs from many other pot-related research projects that are focused on chronic, heavy users of cannabis. [Other studies have revealed brain changes among heavy marijuana users, but this research is believed to be the first to demonstrate such abnormalities in young, casual smokers.]

The collaborative effort between Northwestern University’s medical school, Massachusetts General Hospital and Harvard Medical School showed a direct correlation between the number of times users smoked and abnormalities in the brain.

“What we’re seeing is changes in people who are 18 to 25 in core brain regions that you never, ever want to fool around with,” said co-senior study author Dr. Hans Beiter, professor of psychiatry and behavioral sciences at Northwestern University. [CORRECTION: Rueters notes the name of researcher is Breiter, not Beiter]

In particular, the study identified changes to the nucleus accumbens and the nucleus amygdala, regions of the brain that are key to regulating emotion and motivation, in marijuana users who smoke between one and seven joints a week.

The researchers found changes to the volume, shape and density of those brain regions. But more studies are needed to determine how those changes may have long-term consequences and whether they can be fixed with abstinence, Breiter said.

“Our hypothesis from this early work is that these changes may be an early sign of what later becomes amotivation*, where people aren’t focused on their goals,” he said. [Amotivation is a state of lacking any motivation to engage in an activity, characterized by a lack of perceived competence and/or a failure to value the activity or its outcomes.]

The study, which was funded in part by the National Institute on Drug Abuse and the White House Office of National Drug Control Policy, comes as access to pot is expanding following 2012 votes in Washington state and Colorado to legalize its recreational use. The drug remains illegal under federal law.

Medical pot is allowed in 20 U.S. states.

Pot legalization advocates make the argument that marijuana is safer than alcohol a central part of their campaigns.

Other research has found drinking alcohol alters the brain, Breiter said. But while researchers do not know exactly how the mental rewiring seen in pot users affects their lives, the study shows it physically changes the brain in ways that differ from drinking, he said.

This latest study fits with other research showing marijuana use has significant effects on young people because their brains are still developing, and Breiter said he has become convinced that marijuana should only be used by people under 30 if they need it to manage pain from a terminal illness.

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Background

From a bostonglobe.com report on the study:

“Anything that underscores that there may be structural changes in the brain [from marijuana use] is important,” said Dr. Staci Gruber, an associate psychiatry professor at Harvard Medical School and a director of brain imaging at McLean Hospital.

Gruber’s studies of marijuana smokers have focused on those with longer, more chronic use and have found that those who started smoking at earlier ages, while still in their teens, are less able to perform certain reasoning and decision-making tasks, compared with those who started later in life.

Stuart Gitlow, president of the American Society of Addiction Medicine, said the Mass. General study provides much-needed “hard evidence” of brain changes that appear to match the changes in cognitive skills - thinking and reasoning - that other researchers have demonstrated in marijuana studies.

“We’ve known that people who use marijuana when they’re younger tend to have cognitive abnormalities, but this gives us direct evidence,” he said.

“It’s fairly reasonable to draw the conclusion now that marijuana does alter the structure of the brain, as demonstrated in this study,” Gitlow said, “and that structural alteration is responsible, at least to some degree, for the cognitive changes we have seen in other studies.”