Due to the lack of a biological test, determining which drug will work best in individuals suffering depression is often a game of trial and error. But the process could become less of a guessing game thanks to researchers at UT Southwestern, who have developed a simple blood test that could allow physicians to more successfully prescribe initial drug treatments.

"Currently, our selection of depression medications is not any more superior than flipping a coin, and yet that is what we do," explains lead author in the research Dr Madhukar Trivedi.

Dr Trivedi started his research into the problem more than a decade ago, initially identifying that nearly a third of patients diagnosed with depression don't respond to their first drug treatment and almost 40 percent of patients stop their medications within three months.

"Giving up hope is really a central symptom of the disease," says Dr Trivedi. "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 team's new study revealed a correlation between a patient's C-reactive protein levels (CRP) and the success or failure of specific drug-related depression treatments. Initial study results showed that patients with low CRP levels displayed more effective remission results on a drug called escitalopram, while patients with higher CRP levels achieved better treatment success when the escitalopram was combined with another drug called bupropion.

Dr Trivedi believes these results could be applied to a broader variety of commonly prescribed anti-depressants and is now directing the team's research to identify the role of CRP with other medications. As a test for CRP levels is as simple as a finger-prick blood test, this method could be a cheap and easy process for doctors to integrate into their clinical diagnoses.

CRP levels are not the only biomarker target that scientists have been looking at in the hunt for clear biological identifiers for depression. A compelling study from 2014 found that levels of certain RNA blood markers could determine whether a patient would respond positively to a treatment of cognitive behavioral therapy.

Another study from 2016 showed that elevated levels of glutamate in sensitive areas of the brain were associated with depressive symptoms in patients, pointing towards potential treatments with ketamine as being the most successful in those patients. This diagnostic process was not as straightforward as the CRP finger-prick tests, though, involving a more complex brain imaging technique called magnetic resonance spectroscopy (MRS).

All of these studies are still in relatively nascent research stages, but they bode well for better understandings of how to diagnose and treat depressed patients more accurately in the future.

The new UT Southwestern research was recently published in the journal Psychoneuroendocrinology.

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