A simple blood test might help patients find the right antidepressant

Anti-depressants don't work for everyone, and sometimes it takes several attempts before finding the right medication. Now researchers say it may be possible to find out if an antidepressant will work with a simple blood test.

Loyola university researchers, for the first time, say it may be possible to predict the effectiveness of the medications by checking a level of a blood protein called vascular endothelial growth factor (VEGF).

In their study the researchers found 85% of patients who had elevated levels of VEGF responded well to the medication escitalopram (Lexapro). Conversely, just 10% of people with lower VEGF levels experienced relief from depression with escitalopram use.

Escitalopram is an SSRI (selective serotonin reuptake inhibitor) that should theoretically relieve depression because it restores chemical balance. Another theory is that SSRI’s help regenerate areas of the brain in depressed people that are no longer active through a process called neurogenesis

Escitalopram stimulates new blood vessel growth, fueled by VEGF; supporting the neurogenesis theory.

"This would be the first time we would have a predictor for how well a patient would respond to an antidepressant," said Angelos Halaris, MD, PhD, first author of the study, during the 2011 annual meeting of the Society of Biological Psychiatry and the 4th Annual Illinois Brain, Behavior and Immunity Meeting.

Halaris says it would be helpful to know which antidepressants will work in patients before they are prescribed, given statistics that 60 percent of patients taking medication fail to fully respond.

In the study, the researchers found patients with higher levels of VEGF had more brain regeneration that correlated with relief of depression.

If the finding is confirmed, physicians could use the blood test to know which antidepressants will work on a patient.