Blood tests that measure the aging of certain white blood cells can predict cognitive and mood-related symptoms of depression, rather than physical symptoms.
The survey results are Journals of Gerontology, Series A: Biological Sciences and Medicineresearchers are closer to identifying a biomarker to detect the mood disorder, which affects nearly one in five adults in the United States.
Depression is diagnosed based on self-reported symptoms. Clinicians may order blood tests to rule out other health conditions, but researchers have not yet identified objective diagnostic biomarkers that can tell early that someone is experiencing depression.
Additionally, depression may go unrecognized because its symptoms go far beyond sadness. Some people may experience physical (or somatic) symptoms such as fatigue, loss of appetite, and agitation. Other symptoms can affect mood and cognition, such as feelings of hopelessness and anhedonia, which means being unable to feel pleasure or losing interest in activities you previously enjoyed.
“Depression is not a one-size-fits-all disease and can look very different from person to person, which is why it’s so important to consider a range of symptoms and not just a clinical label,” said study author Nicole Beaulieu-Perez, an assistant professor at New York University’s Rory Myers College of Nursing.
Our study revealed the unique biological underpinnings of mental health that are often obscured by broad diagnostic categories. ”
Nicole Beaulieu Perez, Rory Myers College of Nursing, New York University
Depression is common in people with certain diseases that affect the immune system, such as HIV. This may be the result of a combination of factors, including chronic levels of inflammation, stigma, and socio-economic factors. Women with HIV have particularly high rates of depression, which may make it more difficult for them to participate in treatment and adhere to antiretroviral therapy.
“For women with HIV who may be experiencing depression, we want to better understand what’s going on and catch it early so it doesn’t negatively impact their overall health,” Perez said.
To investigate the biological basis of depression in HIV-infected and uninfected women, researchers examined measures of accelerated biological aging that are associated with both depression and HIV. Biological age, which may differ from your actual age, can be assessed using an “epigenetic clock,” an algorithm that captures chemical modifications in your DNA.
Researchers analyzed data from 440 women (261 with HIV and 179 without HIV) who participated in the Women’s Interagency HIV Study. Depression was measured using the Center for Epidemiological Studies Depression Scale (CES-D), a 20-item questionnaire that examines both somatic and non-somatic symptoms.
They also used blood samples to assess biological aging using two different epigenetic clocks. One measured multiple cell and tissue types, and the other focused on a type of white blood cell called monocytes. Monocytes are involved in various immune responses and play an important role in HIV infection, and they have been shown to be increased in depressed patients.
Researchers found that monocyte aging is a sensitive biomarker of non-somatic symptoms of depression, particularly anhedonia, feelings of hopelessness and failure, in women with and without HIV infection.
“This is particularly interesting because people with HIV often present with physical symptoms such as fatigue that are caused by a chronic illness rather than a diagnosis of depression. But this turns that idea on its head, as we found that these measures were related to mood and cognitive symptoms, rather than physical symptoms,” Perez said.
Measures of depression were not associated with other epigenetic clocks that use multiple cell and tissue types.
Perez cautions that more research is needed into epigenetic aging and depression before we can figure out how to measure and treat depression. In the long term, developing biomarker tests for depression could allow for earlier diagnosis and potentially more personalized treatment, for example by predicting which drugs will be most effective based on an individual’s profile.
“We think about the adage ‘what gets measured gets managed.’ An ambitious goal in mental health would be to combine subjective experience with objective biological testing,” Perez said. “Our findings bring us one step closer to this goal of precision mental health care, especially for high-risk populations, by providing a biological framework that may guide future diagnosis and treatment.”
