Scientists are developing a new approach to identifying depression by observing the deterioration of certain immune cells. A new study by researchers from New York University suggests that physical changes in certain immune cells (white blood cells) hold potential as an indicator for the emotional and cognitive changes in depression. The result can mean new methods for early detection through blood tests.
This research, published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences, links the process of biological aging within immune cells to specific ways that depressive symptoms manifest in older people. While these findings do not identify a diagnostic blood test for depression, they add to growing evidence that the immune system could give scientists a way to measure mental health.
The human immune system changes over a person’s life, and some of these changes can be measured through epigenetics. Epigenetics are chemical marks that change how genes are expressed but do not change the DNA sequence itself.
This offers researchers the ability to determine a person’s biological age, which could be older or younger than their physical age. To do this, researchers typically measure epigenetic changes using technology called epigenetic clocks.
In this study, the researchers looked at monocytes, immune cells that are primed by the body to respond to infection, inflammation, and other risks. The researchers looked to see if faster biological aging in these cells was related to particular symptoms of depression.
The results indicated that increased monocyte age acceleration correlated with non-physical depressive symptoms anhedonia, hopelessness, and the feeling of failure. Anhedonia refers to a loss of interest or reduced ability to feel pleasure from something, which a person has previously taken interest in and enjoyed.
It is notable still that the investigators did not observe a link between monocyte aging and physical symptoms of depression, like appetite or fatigue. This may indicate that different components of depression have different underlying biological links.
The research team examined data from 440 women involved in the Women’s Interagency HIV Study. Among these women, 261 had HIV and 179 did not have the virus.
Researchers evaluated participants’ depressive symptoms using a standardized questionnaire and analyzed DNA methylation patterns to estimate biological aging. They compared a clock specific to monocytes with another that measures aging across various cell and tissue types.
The measure specific to monocytes was connected to non-somatic depressive symptoms in the entire sample. The association was driven by anhedonia. In contrast, the overall measure of biological aging was not linked to severity of depression or any of the types of symptoms.
So looking at this specific immune cell may be able to provide information that the other, wider measures of biological aging do not. But, the effects were relatively modest and not entirely consistent across groups, and more research is needed before researchers can assess how well the approach might work more broadly.
For instance, a person might have a loss of motivation, feeling hopeless and losing interest in things without knowing they are depressed. A biological measurement might help scientists to develop a better understanding of these sort of cases and whether the various symptom combinations have different biological origins.