Blood Test Predicts Efficacy of Antidepressants

As about 60% of depressed patients do not respond fully to the first prescribed medication, doctors often must prescribe a different medication before finding one that works.

The Loyola study involved 35 patients who took a selective serotonin reuptake inhibitor (SSRI) for major depressive disorder. Scientists are not certain why SSRIs work in some patients but not in others. One possible mechanism is that SSRIs help restore a chemical balance in the brain. Some scientists recently have proposed a second possible mechanism, called neurogenesis, suggesting SSRIs help to regenerate brain cells in specific parts of the brain that have atrophied in depressed patients.

The Loyola study supports the neurogenesis theory. It appears that the SSRI used in the Loyola study, jump-starts brain cells that have become inactive. This regeneration is fueled by VEGF. In the brain, VEGF stimulates the growth of blood vessels and works in other ways to keep brain cells healthy and active. It appears that in patients with higher levels of VEGF, there was more regeneration, helping to reduce depression. Conversely, in patients with lower VEGF levels, there was less regeneration of brain cells and less relief from depression. If the finding is confirmed by further studies, it could lead to a blood test that would help physicians tailor treatment.

Angelos Halaris, MD, PhD, first author of the study said, "Currently, a VEGF blood test would be quite expensive if it were performed for a patient. But the cost likely would come down significantly if a VEGF test were to become widely used.” The results of the a study were presented during the annual meeting of the Society of Biological Psychiatry and the 4th Annual Illinois Brain, Behavior and Immunity Meeting held in December 2011.

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Loyola University Medical Center