Could a Blood Test Reveal Depression?

Depression is a mental health disorder that affects millions of people in the U.S. Individuals who have depression experience changes in mood, such as persistent sadness, anxiety, and empty feelings; sleep or eating disruptions; and suicidal thoughts or actions. Depression can vary along a continuum from mild to very severe.

Diagnosing Depression

Unfortunately, your physician does not have a test that definitively diagnoses depression, so he takes a multi-pronged approach. A physical exam and lab tests help rule out medications or other medical conditions that can cause depression-like symptoms. During the psychological evaluation, he'll learn about your family's history of depression and mental illness, your symptom severity, frequency, and duration, and your history (if any) of substance abuse and suicidal thoughts.

Potential New Test?

Mental health professionals would welcome additional tools to help them accurately diagnose depression, especially major depressive disorder.

A recent pilot study with a very small sample evaluated a potential blood test designed to help clinicians diagnose depression. Researchers measured levels of nine biomarkers in patients previously diagnosed with major depressive disorder and in another group of non-depressed individuals. Biomarkers are specific physical traits used to measure the effects or progress of a medical condition. Researchers believe these biomarkers are altered in adults with major depressive disorder, thus possibly making it a target for a diagnostic test. The test accurately pinpointed depression in 90 percent of the depressed patients.

One of the goals of such a test is to remove the stigma and shame of depression and encourage more sufferers to seek treatment. There are downsides, however. For example, if a depressed patient has a negative test result, he may not get the help he needs.

On his blog, psychiatrist James Amos, M.D. notes that the diagnostic firm that developed this test also funded the study, which may potentially create a conflict of interest. He also says that because depression is more complex than many other diseases, mental health professionals rely on a combination of evaluation tools, including standardized rating scales, to make a diagnosis.

A neuroscientist in the United Kingdom, who is also a skeptic, warns on his blog that a diagnostic test must be able to distinguish depression from other, related, diseases (such as bipolar disorder, for example) to be useful. He says that in practice, physicians are more likely to have to make these distinctions rather than differentiating depressed individuals from those who are healthy.


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National Institute of Mental Health. "How Is Depression Diagnosed and Treated?" Web. 27 July 2011.