Roughly 10 percent of American adults suffer from depression — yet health experts are still often stumped by the best ways to treat it. Part of the problem lies in the fact that no two patients suffer from exactly the same symptoms, nor will they have the same reaction to medication, or the same treatment outcome. The other part of the problem is that doctors are just beginning to understand all of the changes that take place in the brain when a person is depressed.

New research may shed some light on this understanding. The study, published in the journal Current Biology, found that selective serotonin reuptake inhibitors (SSRIs) — a popular type of antidepressant medication used to treat depression — may alter the way the brain communicates in as little as one dose. (SSRIs include popular antidepressants such as Prozac, Lexapro, Celexa, Paxil and Zoloft.)

For the study, researchers at the Max Planck Institute in Leipzig, Germany, used MRIs to compare connections in the gray matter of those participants who took SSRIs and those who did not. They first tracked the brain activity of patients without medication, scanning the participants while their brains thought about nothing specific for about 15 minutes. Next, the researchers gave the study participants a single dose of an SSRI and performed the brain scan again.

They found that even one dose of this type of antidepressant reduced connectivity in most parts of the brain, but increased connectivity within the cerebellum and thalamus — the parts of the brain associated with motor control and signal regulation — within just a few hours.  

Researchers still don't know what this type of brain activity might have to do with regulating depression, but they are hopeful that this study may one day help doctors understand which type of medication a person with depression is most likely to respond to.

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