Major depressive disorder (MDD) is the most prevalent psychiatric disorder which can go under-diagnosed or misdiagnosed. It affects 6.7 percent of the U.S. adult population in a year. The current method of diagnosing depression is subjective and based on non-specific symptoms such as poor mood, fatigue and change in appetite, all of which can apply to a large number of mental or physical problems. A diagnosis also relies on the patient’s ability to report his symptoms and the physician’s ability to interpret them. But depressed patients frequently under report or inadequately describe their symptoms. Hence, there is a need for a clinically validated diagnostic test that can assure correct and timely diagnosis.