Psychiatric Medicine

The Holy Grail of Diagnosing Depression - An Effective Blood Test

By Martin S. Lipsky, MD

Adjunct Professor, Institute on Aging, School of Community Health, Portland State University; Dean Emeritus, University of Illinois College of Medicine, Rockford

SYNOPSIS:  As depression’s diagnosis is inherently subjective, an objective diagnostic tool would be a marked improvement. This study analyzed nine different biomarkers and potentially paves the way for a blood test that can identify depressed patients.

SOURCE: Redei EE, et. al. Blood transcriptomic biomarkers in adult primary care patients with major depressive disorder undergoing cognitive behavioral therapy. Transl Psychiatry 2014;4,e442 published online September 2014. 

Nearly 6.7% of the population is afflicted with major depressive disorder (MDD). A complex psychiatric disease with serious ramifications, depression’s diagnosis nonetheless currently relies primarily on self-reported symptoms and medical provider evaluation, a process compromised by depressive patients’ tendency to underreport or mischaracterize symptoms. Moreover, there are differences among commonly used depression scales that could lead to potential misdiagnosis. That only half of depressive patients in the US are properly recognized and treated, then, is a somber but unsurprising reality.

Given the problems with depression’s current diagnostic mechanisms, an objective test like a blood test that could effectively, accurately and repetitively reveal MDD would be a huge improvement. Redei et al analyzed nine different RNA transcript blood marker that were highlighted as important in prior tests of depression in animals in order to test if these markers would differentiate depressive patients from non-depressive controls. In a matched pairs pilot study lasting 18 weeks, Redei and her team studied 64 patients, 32 of which were diagnosed with MDD and undergoing cognitive behavioral therapy, and 32 non-depressed, age-matched controls. Excluding patients who had recently undergone anti-depressant pharmacotherapy as well as patients with hearing or vision problems, substance abuse, or other psychiatric illnesses, the study attempted to remove many potentially confounding variables.

The baseline blood marker levels of the two groups differed significantly. Biomarkers were tested again at the 18-week mark of cognitive behavioral therapy, and patients who had responded to CBT and were deemed no longer depressed by the traditional method of clinical interview/self-reported symptoms astoundingly had different results from those patients who remained depressed.

Based on these findings, the authors could conclude that the blood marker levels of various transcript panels can aid in the successful differentiation of the depressed from the non-depressed as well as perhaps even predict/monitor a patient’s response to cognitive behavioral therapy.