More 'joints' equal more damage
The size and shape of
two brain regions involved in emotion and motivation may differ in young adults
who smoke marijuana at least once a week, according to a study published April
16 in The Journal of
Neuroscience.
The findings suggest that recreational marijuana use may
lead to previously unidentified brain changes, and highlight the importance of
research aimed at understanding the long-term effects of low to moderate
marijuana use on the brain.
Marijuana is the most
commonly used illicit drug in the United States, with an estimated 18.9 million
people reporting recent use, according to the most current analysis of the
National Survey on Drug Use and Mental Health.
Marijuana use is often
associated with motivation, attention, learning, and memory impairments.
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However, less is known about how low to moderate marijuana use affects brain
structure in people, particularly in teens and young adults.
In the current study,
Jodi Gilman, PhD, Anne Blood, PhD, and Hans Breiter, MD, of Northwestern
University and Massachusetts General Hospital/Harvard Medical School used
magnetic resonance imaging (MRI) to compare the brains of 18- to 25-year olds
who reported smoking marijuana at least once per week with those with little to
no history of marijuana use.
Although psychiatric evaluations ruled out the
possibility that the marijuana users were dependent on the drug, imaging data
revealed they had significant brain differences. The nucleus accumbens -- a
brain region known to be involved in reward processing -- was larger and
altered in its shape and structure in the marijuana users compared to
non-users.
"This study
suggests that even light to moderate recreational marijuana use can cause
changes in brain anatomy," said Carl Lupica, PhD, who studies drug
addiction at the National Institute on Drug Abuse, and was not involved with
this study. "These observations are particularly interesting because
previous studies have focused primarily on the brains of heavy marijuana smokers,
and have largely ignored the brains of casual users."
The team of scientists
compared the size, shape, and density of the nucleus accumbens and the amygdala
-- a brain region that plays a central role in emotion -- in 20 marijuana users
and 20 non-users.
Each marijuana user was asked to estimate their drug
consumption over a three-month period, including the number of days they smoked
and the amount of the drug consumed each day. The scientists found that the
more the marijuana users reported consuming, the greater the abnormalities in
the nucleus accumbens and amygdala.
The shape and density of both of these
regions also differed between marijuana users and non-users.
"This study raises
a strong challenge to the idea that casual marijuana use isn't associated with
bad consequences," Breiter said.
This research was
funded by the National Institute on Drug Abuse, the Office of National Drug
Control Policy, Counterdrug Technology Assessment Center, and the National
Institute of Neurological Disorders and Stroke.
Story Source:
The above story is
based on materials provided
by Society for Neuroscience (SfN).Note:
Materials may be edited for content and length.
Journal
Reference:
1.
Jodi M. Gilman, John K. Kuster, Sang Lee, Myung Joo Lee, Byoung
Woo Kim, Nikos Makris, Andre Van Der Kouwe, Anne J. Blood and Hans C. Breiter. Cannabis Use is Quantitatively
Associated with Nucleus Accumbens and Amygdala Abnormalities in Young Adult
Recreational Users. Journal
of Neuroscience, April 16, 2014 (in press)
Cite This Page:
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Society for Neuroscience
(SfN). "Brain changes associated with casual marijuana use in young
adults: More 'joints' equal more damage." Science Daily, 15 April 2014.
<www.sciencedaily.com/releases/2014/04/140415181156.htm>.