A simple blood test may be able to detect depression, according to a recent study.

Blood tests for mental illnesses have until recently been regarded as impossible, but researchers from the Medical University of Vienna have demonstrated the possibility of detecting depression in a laboratory analysis of a blood sample.    

"This is the first study that has been able to predict the activity of a major depression network in the brain using a blood test," Lukas Pezawas, leader of the study, said in a statement. "This study clearly shows that a blood test is possible in principle for diagnosing depression and could become reality in the not too distant future."

Serotonin transporter (SERT) is a protein in the cell membrane that facilitates the transport of the neurotransmitter serotonin (popularly known as the "happiness hormone") into the cell, researchers said. In the brain, serotonin transporter regulates neural depression networks. Depressive conditions can frequently be caused by a lack of serotonin.

Recent studies have shown that the serotonin transporter in the blood works in exactly the same way as in the brain. In the blood, it ensures that blood platelets maintain the appropriate concentration of serotonin in the blood plasma.

Researchers have used functional magnetic resonance imaging of the brain and pharmacological investigations to demonstrate that there is a close relationship between the speed of the serotonin uptake in blood platelets and the function of a depression network in the brain.

The depression network is termed the "default mode network because it is primarily active at rest and processes content with strong self-reference.

"Findings from recent years have also demonstrated that it is actively suppressed during complex thought processes, which is essential for adequate levels of concentration," researchers said.

The research indicates that the diagnosis of depression through blood tests could become reality in the not too distant future.