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
The study to be published on Wednesday in the
Journal of Neuroscience differs from many other pot-related research
projects that are focused on chronic, heavy users of cannabis.
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.
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, Beiter 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.
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.
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, Beiter
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
This latest study fits with other research showing marijuana use has
significant effects on young people because their brains are still
developing, and Beiter 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.
(Reporting by Alex Dobuzinskis; Editing by Ken Wills)