A single dose
of a popular class of psychiatric drug used to treat depression can alter the
brain’s architecture within hours, even though most patients usually don’t
report improvement for weeks, a new study suggests.
More than 1
in 10 adults in the U.S. use these drugs, which adjust the availability of a
chemical transmitter in the brain, serotonin, by blocking the way it is
reabsorbed. The so-called Selective Serotonin Reuptake Inhibitors, or SSRIs,
include Prozac, Lexapro, Celexa, Paxil and Zoloft.
The findings
could be a first step toward figuring out whether a relatively simple brain
scan might one day help psychiatrists distinguish between those who respond to
such drugs and those who don’t, an area of mystery and controversy in
depression treatment.
Researchers
at the Max Planck Institute in Leipzig, Germany, used a magnetic resonance
imaging machine to compare connections in the gray matter of those who took
SSRIs and those who did not. They were particularly interested in what goes on
when the brain is doing nothing in particular.
When more
serotonin was available, this resting state functional connectivity decreased
on a broad scale, the study found. This finding was not particularly surprising
-- other studies have shown a similar effect in brain regions strongly
associated with mood regulation. But there was a two-fold shock: Some areas of
the brain appeared to buck the trend and become more interdependent. And all
the changes were evident only three hours after the single dosage!
Most people
who use antidepressants don't report any discernible change in mood for at
least two weeks. The rapid connectivity shifts noted by the study might
therefore be precursors to longer-term changes, perhaps starting with
remodeling of synapses, the microscopic gaps where chemical neurotransmitters
such as serotonin flood across to an adjacent brain cell, the study suggests.
But this type of brain scanning can’t pick up changes at such a scale, so the hypothesis
will have to be tested other ways.
Study subjects did not have diagnoses of depression, so researchers will
need to generate similar maps among those diagnosed with depression, and re-map
them during and after depressive episodes, as well as after treatment.
Comparisons might then show whether a certain initial architecture predicts
treatment success. “In a perfect world, you would look not only at SSRIs, but
all sorts of medications and non-pharmacological interventions,” Dr Sacher, one
of the researchers said.
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