Soon there may be a blood test to diagnose depression. There are many factors that can cause depression, and genetics can play a role. Recently, a study published in Biological Psychiatry has identified a set of blood markers believed to be the “genetic signature” of major depressive disorder (MDD).
All genes result in the production of molecules — such as RNA and proteins — that can usually be detected in the blood. RNA molecules are direct transcriptions of the DNA messages contained in genes — kind of like photocopying a page from a book. This knowledge has lead scientists to suspect that they can develop blood tests to detect the presence of most heritable disorders, including depression.
Unlike other illnesses like diabetes and heart disease, there are no blood tests to determine if a patient definitively has depression. The diagnosis of psychological disorders is frequently complicated by the fact that symptoms are often self-reported by patients and therefore are highly subjective. This can lead to misdiagnoses when patients misunderstand or are uncomfortable revealing the true nature of their symptoms.
To accomplish their research, the scientists enrolled 34 patients with MDD for the experimental group and 35 healthy patients for the control group. For their primary experiment, they extracted blood from 21 MDD patients and 21 healthy patients. After a period of incubation, they extracted the RNA molecules contained in each patient’s blood. Finally, the researchers compared the RNA molecules extracted from the blood of MDD patients to those extracted from the blood of healthy patients.
The results showed a set of seven gene products present in the blood of MDD patients, but not in healthy patients. To verify their results, the researchers used blood from the remaining subjects — 12 with MDD and 13 healthy–to run the test with a more commonly used and less expensive DNA amplification method called polymerase chain reaction (PCR). Once again, they found the same seven markers in the MDD patients and not in the healthy ones. The researchers are therefore confident that they found a set of detectable markers that can be used as a simple blood test to confirm a diagnosis of heritable MDD.
People with MDD can suffer major setbacks in life because of the psychological, physical, and social impairments the condition causes. In the long run, this test may reduce the rate of MDD misdiagnosis and improve the quality and availability of care for those who truly suffer from the disorder.