Doctors for the first time can determine which medication is more likely to help a patient overcome depression, according to research that pushes the medical field beyond what has essentially been a guessing game of prescribing antidepressants.

A blood test that measures a certain type of protein level provides an immediate tool for physicians who until now have relied heavily on patient questionnaires to choose a treatment, said Dr. Madhukar Trivedi, who led the research at UT Southwestern Medical Center for Depression Research and Clinical Care.

Currently, our selection of depression medications is not any more superior than flipping a coin, and yet that is what we do. Now we have a biological explanation to guide treatment of depression, said Dr. Trivedi, Director of the depression center, a cornerstone of UT Southwestern Peter O Donnell Jr. Brain Institute.

The study demonstrated that measuring a patient C–reactive protein (CRP) levels through a simple finger–prick blood test can help doctors prescribe a medication that is more likely to work. Utilizing this test in clinical visits could lead to a significant boost in the success rate of depressed patients who commonly struggle to find effective treatments. A major national study Dr. Trivedi led more than a decade ago (STAR*D) gives insight into the prevalence of the problem: Up to a third of depressed patients dont improve during their first medication, and about 40 percent of people who start taking antidepressants stop taking them within three months.

This outcome happens because they give up, said Dr. Trivedi, whose previous national study established widely accepted treatment guidelines for depressed patients. Giving up hope is really a central symptom of the disease. However, if treatment selection is tied to a blood test and improves outcomes, patients are more likely to continue the treatment and achieve the benefit.

The new research published in Psychoneuroendocrinology measured remission rates of more than 100 depressed patients prescribed either escitalopram alone or escitalopram plus bupropion. Researchers found a strong correlation between CRP levels and which drug regimen improved their symptoms:

• For patients whose CRP levels were less than 1 milligram per liter, escitalopram alone was more effective: 57 percent remission rate compared to less than 30 percent on the other drug.
• For patients with higher CRP levels, escitalopram plus bupropion was more likely to work: 51 percent remission rate compared to 33 percent on escitalopram alone.

Dr. Trivedi noted that these results could readily apply to other commonly used antidepressants.