Blood tests that track how certain white blood cells age may help identify depression, focusing on emotional and cognitive symptoms rather than physical symptoms.
This study Journals of Gerontology, Series A: Biological Sciences and MedicineThis brings scientists closer to finding a reliable biological marker for depression, a condition that affects nearly one in five adults in the United States.
Blood-based clues may improve depression diagnosis
Currently, depression is diagnosed based on what patients report about their symptoms. Although doctors may order laboratory tests to rule out other illnesses, there is still no objective biological test that can confirm depression or detect depression early.
One problem is that depression isn’t the same for everyone. Some people experience physical (or somatic) symptoms such as fatigue, changes in appetite, and restlessness, while others primarily suffer from emotional and cognitive effects. These may include feelings of hopelessness, difficulty thinking clearly, or an inability to feel pleasure and loss of 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 School of Nursing. “Our study reveals the unique biological underpinnings of mental health that are often obscured by broad diagnostic categories.”
Depression, immune health, and HIV
Depression is especially common in people with immune-related diseases such as HIV. This higher risk may be due to a combination of chronic inflammation, social stigma, and economic challenges. Women living with HIV are particularly affected, and depression can interfere with their ability to stay engaged in treatment and take antiretroviral medications consistently.
“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.
Research on biological aging using epigenetic clocks
To better understand the biology behind depression, researchers looked at signs of accelerated aging within the body. Biological age does not necessarily correspond to a person’s chronological age, but can be estimated using an “epigenetic clock.” These tools measure chemical changes in DNA that occur over time.
The study included 440 women (261 living with HIV and 179 uninfected with HIV) from the Women’s Interagency HIV Study. Depressive symptoms were assessed using the Center for Epidemiological Studies Depression Scale (CES-D), a 20-item questionnaire that assesses both somatic and non-somatic symptoms.
Blood samples were also analyzed to measure biological aging using two types of epigenetic clocks. One assessed aging across multiple cell types and tissues, and the other focused specifically on monocytes, a type of white blood cell involved in the immune response. Monocytes play an important role in HIV infection and are often elevated in patients with depression.
Aging of immune cells is associated with emotional symptoms
The results showed that monocyte aging is strongly associated with non-somatic symptoms of depression. These included anhedonia, hopelessness, and feelings of failure in both HIV-infected and uninfected women.
“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.
In contrast, a broader epigenetic clock that measured multiple cell types showed no association with depressive symptoms.
Towards early detection and personalized treatment
Perez emphasized that further research is needed to translate these findings into clinical care. Still, the results point to a future in which biological tests can detect depression earlier and more accurately.
Such advances could ultimately support more individualized treatment approaches, such as identifying which drugs are most effective for specific individuals.
“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.”
Other study authors include Ke Xu of Yale University; Yanxun Xu, Lang Lang, Gypsyamber D’Souza, and Leah Rubin from Johns Hopkins University; Kathryn Anastos of Albert Einstein College of Medicine; Maria Alcaide of the University of Miami Miller School of Medicine; Marge Cohen of Stroger Hospital, Cook County Health System; Sudeep Shrestha of the University of Alabama at Birmingham. Andrew Edmonds of UNC-Chapel Hill. Jacqueline Myers of Downstate Health Sciences University; Sable Kasaye of Georgetown University; Igo Ofokun of Emory University; and Bradley Awizerat of New York University.
This research was supported by the National Institute of Mental Health (F32MH129151, P30MH075673) and the National Institute on Minority Health and Health Disparities (K08MD019998).
