A single dose of antidepressants is enough to produce significant changes in brain function.
Researchers took brain scans of people before and after taking an acute dose of the antidepressant SSRI (serotonin reuptake inhibitor) and noticed significant differences after a period of only three hours, Cell Press reported.
"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," said Julia Sacher of the Max Planck Institute for Human Cognitive and Brain Sciences.
SSRIs are one of the most widely used antidepressants across the globe; despite extensive studies researchers are still not sure exactly how they work. The drugs most likely affect brain connectivity, but it is commonly believed these changes take weeks of treatment to set in. The new findings suggest key changes actually start to occur soon after the drug is administered.
To make their findings the researchers asked study participants to let their minds wander for 15 minutes while in a brain scanner that assessed the oxygenation of blood flow to the brain. The team looked at three-dimensional images of the patients' brains by measuring the number of connections between voxels, which can be compared to pixels in an image. The researchers observed changes in these connections after only a single dose of the drug escitalopram, which goes by the trade name Lexapro.
The scans showed one dose of the common depression drug reduced the levels of "intrinsic connectivity" in almost the entire brain, but increased the connectivity in two key regions: the cerebellum and thalamus.
Future studies along these lines could help researchers gain insight into the brains of patients suffering from depression. In their next trials they hope to compare the "functional connectivity signature" in the brains of those recovering from depression and patients who do not respond to SSRI treatment.
"[These findings] could help to better predict who will benefit from this kind of antidepressant versus some other form of therapy," Sacher said. "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."
The findings were published Sept. 18 in the journal Current Biology
