A simple blood test may be enough to diagnose depression and quickly determine whether antidepressant drugs are working, researchers said Tuesday.

That’s because scientists have identified a protein in the brain that can serve as a biomarker for depression, according to a study published in the Journal of Neuroscience.

“This test could serve to predict the efficacy of antidepressant therapy quickly, within four to five days, sparing patients the agony of waiting a month or more to find out if they are on the correct therapeutic regimen,” said lead author Mark Rasenick of the University of Illinois at Chicago College of Medicine.

Rasenick and his colleagues studied the brains of 16 clinically depressed people who committed suicide and compared them to the brains of cadavers with no history of psychiatric disorders.

They found that a larger proportion of the key signaling protein Gs alpha was trapped in a part of the brain cells called lipid rafts, confirming earlier studies in rats and brain cell cultures.

“These ‘rafts’ are thick, viscous, almost gluey areas, that either facilitate or impede communication between membrane molecules,” Rasenick said. When this protein becomes trapped in the rafts its ability to activate neurotransmitters is reduced.

“Antidepressants help to move the Gs alpha out of these rafts and facilitate the action of certain neurotransmitters.” While it takes about a month for antidepressants to impact the brain, Rasenick found a change could be observed in blood cells in just four or five days.

“The test that could be developed for all this is a very simple one that could be done in a clinical laboratory,” he said. “We’re very excited with the possibility that in four or five days we’d be able to determine whether an individual was getting the appropriate therapy and if not we could switch therapy.” afp