A blood test for depression has long been out of reach. New research from New York University suggests it may be getting closer, by tracking how quickly certain immune cells age.
The study found that accelerated aging in monocytes, a type of white blood cell, was closely linked to emotional and cognitive symptoms of depression, including hopelessness, loss of pleasure and feelings of failure. It did not show the same link with physical symptoms such as fatigue.
The research was published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences.
Today, depression is diagnosed based on what patients report about their symptoms. Doctors may order lab tests to rule out other illnesses, but there is still no objective biological test that can confirm depression or detect it early.
Part of the problem is that depression does not look the same for everyone. Some people have physical, or somatic, symptoms such as fatigue, appetite changes or restlessness. Others mainly experience emotional and cognitive effects, including hopelessness, difficulty thinking clearly or anhedonia, the inability to feel pleasure and loss of interest in previously enjoyed activities.
“Depression is not a one-size-fits-all disorder, it can look really different from person to person, which is why it’s so important to consider varied presentations and not just a clinical label,” said study author Nicole Beaulieu Perez, assistant professor at NYU Rory Meyers College of Nursing. “Our study reveals unique biological underpinnings of mental health that are often obscured by broad diagnostic categories.”
The study included 440 women, 261 living with HIV and 179 without HIV, from the Women’s Interagency HIV Study.
Researchers assessed depression symptoms using the Center for Epidemiologic Studies Depression Scale, a 20-item questionnaire that evaluates both somatic and non-somatic symptoms. They also analysed blood samples using two types of epigenetic clocks, tools that estimate biological age by measuring chemical changes to DNA over time.
One clock assessed aging across multiple cell types and tissues. The other focused on monocytes, which play a role in immune responses and are often elevated in people with depression.
The findings showed that monocyte aging was strongly associated with non-somatic symptoms of depression in both women with and without HIV. The broader epigenetic clock measuring multiple cell types did not show a link to depression symptoms.
“This is particularly interesting because people with HIV often have physical symptoms like fatigue that are attributed to their chronic illness rather than a depression diagnosis. But this flips that on its head because we found that these measures are associated with mood and cognitive symptoms, not somatic symptoms,” Perez said.
Depression is especially common among people with immune-related conditions such as HIV, according to the researchers. The study says women living with HIV are particularly affected, and depression can interfere with their ability to stay engaged in care and consistently take antiretroviral medications.
“For women with HIV who may be experiencing depression, we want to better understand what’s going on and catch it earlier so that it doesn’t harm their whole overall health,” Perez said.
Perez said more research is needed before the findings could be used in clinical care, but said the results point to the possibility of earlier and more precise detection through biological testing.
“I think about the adage, ‘What gets measured gets managed.’ An aspirational goal in mental health would be to combine subjective experience with objective biological testing,” Perez said. “Our findings bring us a step closer to this goal of precision mental health care, especially for high-risk populations, by providing a biological framework that could guide future diagnosis and treatment.”
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