In the past decade, a great deal of scientific data has been published
about the relationship of the teen brain to drug use. A recent Northwestern
University’s Feinberg School of Medicine and Harvard Medical School
proved that even occasional marijuana use has long-term effects on the
young human brain. “There is this general perspective out there
that using marijuana recreationally is not a problem — that it is
a safe drug,” says Anne Blood, an assistant professor at Harvard
and the co-senior author of the study. “We are seeing that this
is not the case.”
In the experiment, scientists studied young adults ages 18 - 25 who use
marijuana regularly, yet casually, one to four times per week. These individuals
underwent psychiatric tests to ensure they were not dependent on marijuana.
“We looked specifically at people who have no adverse impacts from
marijuana — no problems with work, school, the law, relationships,
no addiction issues,” says Hans Breiter, a professor of psychiatry
and behavioral sciences at Northwestern and co–senior author of
the study. The control group consisted of individuals who do not use marijuana at all.
The study examined two key parts of the brain — the nucleus accumbens
and the amygdala. Together, they help control how people judge things
to be rewarding or aversive and whether they experience pleasure or pain
from experiences. Breiter says that development of these regions is the
key for young people to open their minds to new experiences, like enjoying
new foods, books, or relationships. “These are core, fundamental
structures of the brain,” says Anne Blood. “They form the
basis for how you assess positive and negative features about things in
the environment and make decisions about them.”
In the marijuana users, scientists found statistically significant changes
to the nucleus accumbens and amygdala. Both parts of the brain changed
in shape and density, and there was a direct correlation to the amount
of brain abnormalities and the consistency of the individual’s marijuana use.
“People think a little marijuana shouldn’t cause a problem
if someone is doing O.K. with work or school,” Breiter says. It’s
true. Fifty-nine percent of US citizens think that it is possible to occasionally
smoke marijuana and still be a responsible adult, according to YouGov.
Additionally, NBC & The Wall Street Journal published a poll in 2014,
finding that only 8% of adults think that marijuana is the most harmful
substance to a person’s overall health when compared to tobacco,
alcohol and sugar. However, this study has begun to show that a young
recreational marijuana user may be able to function in society, but their
marijuana use will still have affects on their developing brain.
It is important to note that marijuana use particularly affects teens and
young adults under the age of 25, as the human brain continues to develop
and change until that age. Breiter said, “I’ve developed a
severe worry about whether we should be allowing anybody under age 30
to use pot unless they have a terminal illness and need it for pain.
Alcohol use at a young age also has the same effect. A study just published
in “Alcoholism: Clinical & Experimental Research” studies
the relationship between repeated exposure to alcohol during adolescence
and its effect on learning and memory. Conducted by University Medical
School’s Department of Psychiatry and Behavioral Sciences, the study
exposed adolescent rodents to alcohol in order to examine the cellular
and synaptic impact. “Repeated alcohol exposure … resulted
in long-lasting changes to the region of the brain that controls learning
and memory,” say the researchers. In short, “something happens
during adolescent alcohol exposure that change the way the hippocampus
and other regions of the brain function,” and that ‘something’
is definitely negative.
Whether it’s marijuana, alcohol, or other substances, it is hard
to argue against this irrefutable evidence that exposure to the adolescent
brain causes long-term negative effects.