No More Guessing: Blood Test Predicts Antidepressant Effectiveness

antidepressants and c-reactive protein

Prescribing and taking antidepressants has always been a game of trial and error. What worked for our friends may fail us altogether. It often takes multiple attempts – recalculating dosages or switching medications – before finding an effective treatment.

It’s not surprising when frustrated patients give up, but new research says doctors may be able to narrow down the best medication for their patients. And it’s all tied to a simple blood test.

More Precise Prescriptions

Currently, antidepressants are prescribed based on what we share with our doctors. Once we’ve clued them into our symptoms, lifestyle and concerns about side effects, we’re usually handed a prescription for one or more medications. But even though medical experience and research informs their decision, ultimately it’s anyone’s guess whether the medication will work.

Until now. A specific protein in the blood which indicates inflammation may help doctors decide which antidepressant will be the most effective.

“Currently, our selection of depression medications is not any more superior than flipping a coin, and yet that is what we do,” said Dr. Madhukar Trivedi, who led the study at UT Southwestern Medical Center’s Center for Depression Research and Clinical Care. “Now we have a biological explanation to guide treatment of depression.”

Trivedi and his team measured the pre-treatment levels of C-reactive protein (CRP) in 106 participants with major depressive disorder.

One group was given escitalopram (known by the brand name Lexapro) and a placebo. The second group was given escitalopram and bupropion (brand names include Wellbutrin and Zyban). Patients with low CRP levels responded better to escitalopram alone whereas those with higher CRP levels saw more effectiveness from two medications.

These results indicate a blood test could also be used to prescribe other common antidepressants.

Antidepressants are infamous for their unpleasant side effects, ranging from low sex drive to sweating and lethargy. For now, it doesn’t look like a blood test will predict the presence or severity of side effects – the study noted that side effect outcomes didn’t differ between the two treatment groups.

Overall Results Provide Hope

These new results offer hope to people who have struggled finding the right medication, a process that can feel futile at times. A previous study led by Trivedi more than a decade ago found that up to one-third of depressed patients don’t improve with their first medication, and approximately 40 percent of patients stop taking antidepressants within three months.

“This outcome happens because they give up,” said Trivedi said. “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.”

What Happens Next?

It may not be long before offering up a blood sample becomes a prerequisite for an antidepressant prescription.

“These findings provide evidence that a biological test can immediately be used in clinical practice,” Trivedi said.

Larger studies will be necessary as researchers determine how CRP predicts the effectiveness of other antidepressants. It will also be crucial to identify other markers in the blood, since CRP may not always be an accurate predictor.

Jen Jope