The researchers say that their biomarker blood test could significantly improve rates of success for antidepressant treatments.
Depression is a serious illness that presents with cognitive, mood, and physical symptoms. Globally, it affects more than 300 million people of all ages.
According to the World Health Organization (WHO), depression is "the leading cause of disability worldwide."
Depression is not the same as the short-lived mood reactions we have to everyday life. It can severely impact people's lives at work, at home, and at school.
At its very worst, depression can lead to suicide, which worldwide claims 800,000 lives per year and is the leading cause of death among those aged 15 to 29 years.
National surveys in the United States show that between 2009 and 2012, more than 1 out of 20 people aged 12 years and older reported current depression - defined as having moderate or severe symptoms in the previous 2 weeks.
Biomarker could significantly improve treatment success
Madhukar Trivedi, a professor in the Department of Psychiatry at the University of Texas (UT) Southwestern Medical Center in Dallas and senior author of the new study, says that doctors choosing treatments for depression have to rely heavily on patient questionnaires.
Fast facts about depression
- People living below the poverty line are more likely to have depression.
- Women are more likely to be affected than men.
- Including direct, suicide-related, and workplace costs, depression cost the U.S. $210.5 billion in 2010.
He says that their findings could significantly improve rates of treatment success, and he adds:
"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."
In previous work, Prof. Trivedi - who is also director of the Depression Center at UT Southwestern's Peter O'Donnell Jr. Brain Institute - showed that up to a third of patients with depression do not improve following their first medication, and around 40 percent cease treatment within 3 months.
He says that this is because patients give up: "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," he adds.
In the new study, the team analyzed remission rates in 106 patients with depression who were randomly allocated between two groups.
One group was prescribed the selective serotonin reuptake inhibitor escitalopram alone and the other group was prescribed escitalopram plus bupropion.
From blood tests taken before the treatment, the researchers also had a measure of each patient's baseline blood level of C-reactive protein (CRP).
Baseline CRP predicted treatment success
When they analyzed the results, the researchers found that differences in remission rates correlated to differences in depression medication, depending on baseline CRP levels.
The results showed that patients whose baseline CRP levels were below 1 milligram per liter responded better to escitalopram alone, whereas those with higher levels responded better to the combined medication.
Previous studies have tried to tie CRP to antidepressant success, but Prof. Trivedi says that they were looking at much higher levels of CRP.
He explains that in his view, "you don't need that high of an inflammation to experience the sickness of depression. Even a little inflammation may be sufficient for the patients to experience some of these symptoms of depression."
The team now plans to carry out larger studies to explore the link between CRP and success with other antidepressants, and also to look for other biological markers of depression treatment effectiveness.
"Both patients and primary-care providers are very desperately looking for markers that would indicate there is some biology involved in this disease. Otherwise, we are talking about deciding treatments from question-and-answer from the patients, and that is not sufficient."
Prof. Madhukar Trivedi