SINGLE DOSE OF ANTIDEPRESSANT CHANGES THE BRAIN
A single dose of
antidepressant is enough to produce dramatic changes in the functional
architecture of the human brain. Brain scans taken of people before and after
an acute dose of a commonly prescribed SSRI (serotonin reuptake inhibitor)
reveal changes in connectivity within three hours, say researchers who report
their observations in the Cell Press journal Current
Biology on September 18.
"We were not
expecting the SSRI to have such a prominent effect on such a short timescale or
for the resulting signal to encompass the entire brain," says Julia Sacher
of the Max Planck Institute for Human Cognitive and Brain Sciences.
While SSRIs are among
the most widely studied and prescribed form of antidepressants worldwide, it's
still not entirely clear how they work. The drugs are believed to change brain
connectivity in important ways, but those effects had generally been thought to
take place over a period of weeks, not hours.
The new findings show
that changes begin to take place right away. Sacher says what they are seeing
in medication-free individuals who had never taken antidepressants before may
be an early marker of brain reorganization.
Study participants let
their minds wander for about 15 minutes in a brain scanner that measures the
oxygenation of blood flow in the brain. The researchers characterized
three-dimensional images of each individual's brain by measuring the number of
connections between small blocks known as voxels (comparable to the pixels in
an image) and the change in those connections with a single dose of
escitalopram (trade name Lexapro).
Their whole-brain
network analysis shows that one dose of the SSRI reduces the level of intrinsic
connectivity in most parts of the brain. However, Sacher and her colleagues
observed an increase in connectivity within two brain regions, specifically the
cerebellum and thalamus.
The researchers say
the new findings represent an essential first step toward clinical studies in
patients suffering from depression. They also plan to compare the functional
connectivity signature of brains in recovery and those of patients who fail to
respond after weeks of SSRI treatment.
Understanding the
differences between the brains of individuals who respond to SSRIs and those
who don't "could help to better predict who will benefit from this kind of
antidepressant versus some other form of therapy," Sacher says. "The
hope that we have is that ultimately our work will help to guide better
treatment decisions and tailor individualized therapy for patients suffering
from depression."
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