Study Links Brain Molecule to Risk of Major Depression02/08/11
TUESDAY, Feb. 8 (HealthDay News) -- People whose genetic make-up
produces lower levels of a brain molecule called neuropeptide Y
(NPY) may be at increased risk for major depression, says a new
Previous research has shown that NPY helps people calm down
after experiencing stressful events.
This study found that when exposed to negative stimuli, people
with gene variations that cause them to produce lower levels of NPY
have stronger responses in key brain circuits related to emotion.
This means they have less resilience to stress and a stronger
psychological response to pain; they were also overrepresented in a
population diagnosed with a major depressive disorder, the
The study was published Feb. 7 in the
Archives of General Psychiatry.
"We've identified a biomarker -- in this case genetic variation -- that is linked with increased risk of major depression," senior author Dr. Jon-Kar Zubieta, a professor of psychiatry and radiology, and a research professor at the University of Michigan Molecular and Behavioral Neurosciences Institute, said in a university news release.
"This appears to be another mechanism, independent of previous targets in depression research, such as serotonin, dopamine and norepinephrine," he added.
In the study, researchers used functional magnetic resonance
imaging (fMRI) to look at the brain activity of participants as
they read neutral words (such as "material") negative words
("murderer") or positive words ("hopeful").
Participants who had lower NPY levels showed lots of activity in
the prefrontal cortex, which is involved with processing emotion,
compared to those with higher NPY levels.
"This tells us that individuals with the risk-associated NPY gene variant tend to activate this key brain region more than other people, even in the absence of stress and before psychiatric symptoms are present," said lead study author Dr. Brian Mickey, an assistant professor of psychiatry at the University of Michigan Medical School.
Researchers then injected participants' jaw muscles with a
saline solution that causes brief moderate pain. The level of pain
was adjusted for each person until they rated it a 4 on a 10-point
Participants were asked to describe how they felt before and
after the injection. Participants in the low NPY group reported
more negative emotions both before and after the injection,
suggesting they were more emotionally affected while both
anticipating and thinking about the painful experience later.
The finding may eventually help with early diagnosis and
treatment for depression, including individualized therapies based
on a patient's genetic profile, the researchers said.
The U.S. National Institute of Mental Health has more about
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