The key to more effectively prescribing antidepressants may be in your blood.

Researchers at UT Southwestern Medical Center have discovered a marker called the C-reactive protein, or CRP, which is found in higher concentrations in the blood of people with depression.

Elizabeth Lippard, a psychiatry professor at the Dell Medical School who wasn’t involved in the study, said measuring CRP levels can help patients choose the right antidepressants.

“Biomarkers that can guide treatment — so doctors can screen patients to determine best treatment options — may greatly reduce the amount of time a patient has to live with emotional and physical consequences of their illness,” Lippard said. 

Madhukar Trivedi, a doctor at UT Southwestern who led the research study, said in a press release that up to a third of patients prescribed antidepressants see no improvement with the first medication they take, leading 40 percent of these patients to stop taking antidepressants after three months.

A UT freshman, who wishes to remain anonymous, said she struggled to find an antidepressant that worked for her.

“Every medicine is really different because not everyone who has depression experiences the same severity or symptoms,” she said. “That’s why it’s difficult to find (an antidepressant) that complements their specific issues.”

Doctors often choose antidepressants based on a patient questionnaire. Trivedi said this was like flipping a coin, and has centered his research in finding biological markers of depression.

“Both patients and primary-care providers are very desperately looking for markers that would indicate there is some biology involved in (depression),” Trivedi said in a news release.  “Otherwise, we are talking about deciding treatments from question-and-answer from the patients, and that is not sufficient.”

Trivedi’s recent study found a strong correlation between CRP levels and which drug regimen improved a patient’s symptoms. Participants who had their blood tested and given an antidepressant based on these tests had higher remission rates.

According to Trivedi, this blood test for CRP levels can be used immediately in clinical practice. Trivedi said he also hopes to find markers for depression that are not linked to CRP.

The anonymous student said she appreciates the research being done and hopes new innovations like the blood test can help others suffering from depression.

“It took four years to find something that worked (for me),” she said. “That’s why it’s so important to find the right medicine and the right dosage, so you can continue to live your life the way you want.”