Study Finds Interesting Link Between Inflammatory Responses and Depression

The relationship between inflammatory responses and depression is an area of developing research, as scientists try to learn more about what triggers mental illness, and how it can best be treated.  

A new study, published in Psychological Science, found that people who experience high inflammatory reactivity to socially stressful situations are more likely to develop depressive symptoms.

“We set out to discover why psychological stress, and particularly interpersonal stress, triggers depression in some people but not others,” says lead author and Ohio State University PhD candidate Annelise A. Madison. 

One theory (The Social Signal Transduction Theory of Depression) suggests that those whose bodies mount an exaggerated inflammatory response to a conflict or other social stressor are most at risk for developing depression over time, especially in the face of frequent or recurring stress.

“This theory had not been tested, so we did so among one sample of breast cancer survivors and another sample of healthy adults,” Madison says. 

A Closer Look at the Research 

Madison and her colleagues analyzed data from two studies that included a social stressor and also included assessments of depressive symptoms and inflammatory biomarkers.

In the first study, 43 physically healthy couples gave a blood sample before taking part in a combative 20-minute problem-solving discussion with their partner. After the conflict (90 minutes later and 300 minutes later), two additional blood samples were taken.

The researchers found that those who reported more frequent interpersonal conflict had more intense depressive symptoms one month later, but only if they experienced greater inflammatory reactivity to the conflict.

In the second study, 79 breast cancer survivors gave a blood sample before taking the Trier Social Stress Test, a stress-inducing situation involving two tasks (speech and mental-arithmetic). At 45 minutes and 120 minutes after the stress test, the participants had their blood drawn again.

The researchers found that participants who experienced more loneliness and felt less socially supported typically had heightened depressive symptoms one year after the test. This was particularly true among those with higher inflammatory reactivity.

“We found evidence in support of the Social Signal Transduction Theory of Depression; that is, people who are more physiologically reactive to interpersonal stress and regularly encounter interpersonal stress are most at risk of depressive symptom increases over time,” says Madison. “These findings suggest that we can take steps to reduce depression risk by 1) lowering our physical reactivity to stress via strategies such as regular engagement in mindfulness meditation; or 2) reducing our exposure to interpersonal stress through more skillful navigation of relationships.”

Madison adds that the flipside of the findings is that those who had heightened inflammatory reactivity to stress—which is not ideal—did not necessarily experience worsening depressive symptoms. “They did so only in the context of frequent exposure to interpersonal stress,” she explains. “Therefore, improving the health and quality of our relationships is key for minimizing our risk of depression.” 

Reducing Depression Risk

The researchers hope that further investigation will answer more of the questions concerning who is most at risk for developing depression, and under what circumstances.

“In particular, the timing, duration, and severity of interpersonal stress likely matter and are deserving of further research in relation to depression onset,” Madison says. “This research is important because then we can start identifying those at risk for depression and proactively take steps to reduce the risk when possible. Also, identifying these underlying physiological mechanisms, such as inflammation, will ultimately help us to treat depression more effectively.”

Marriage and family therapist, speaker, and yoga and meditation guide Claudia de Llano recommends mindfulness meditation as a way of stilling the mind. 

This can take many forms, from a conscious walk or activity where you begin to tune into sights, sounds, smells, and sensations, to chanting, sound healing, music, yoga, or breathing exercises.

"When depression is present, we often experience symptoms including feelings of sadness, stagnation, guilt, and a loss of interest," de Llano says. "This can lead to an imbalance of physical and mental energy, overall concentration, and disturbance related to sleep, appetite, sex, and the ability to function in daily life."

Mindfulness specifically allows us to slow the mind down by bringing awareness in a way that interrupts the chain of past and future thinking which are out of our control, de Llano explains. "By connecting to the breath, moving consciously, using sound, and meditating in a way that allows presence, the nervous system relaxes and often brings us into the present moment," she says. "This can have a deep impact soothing the mind and body in a way that is tangible and often pleasant."