According to a new study published in Psychological Sciences. The results provide new insights into how interpersonal stress and inflammatory responses are linked to mental illness.

“We set out to find out why psychological stress, and in particular interpersonal stress, triggers depression in some people but not others,” explained study author Annelise Madison, a doctoral student in clinical psychology at the University. ‘Ohio State University.

“One theory (The Social Signal Transduction Theory of Depression) suggests that those whose body develops an exaggerated inflammatory response to conflict or other social stressor are most at risk of developing depression over time, especially in the face of frequent or recurring stress. This theory had not been empirically tested, so we did it among a sample of breast cancer survivors and another sample of healthy adults.

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 provided a blood sample before engaging in a contentious 20-minute problem-solving discussion with their partner. Two additional blood samples were taken approximately 90 and 300 minutes after the conflict. The researchers found that those who reported more frequent interpersonal conflict had increased depressive symptoms about a month later, but only if they had greater inflammatory reactivity to marital conflict.

In the second study, 79 breast cancer survivors provided a blood sample before taking the Trier Social Stress Test, an experimentally tested stress scenario consisting of a speech and mental arithmetic task. The participants then underwent a new blood test 45 and 120 minutes after the stress test. The researchers found that participants who felt more lonely and less socially supported tended to have increased depressive symptoms one year later, and this was especially true among those who had higher inflammatory reactivity.

“We found evidence to support the social signal transduction theory of depression; that is, people who are more physiologically reactive to interpersonal stress and who regularly experience interpersonal stress are most at risk for increasing depressive symptoms over time,” Madison told PsyPost. “These results suggest that we can take steps to reduce the risk of depression by 1) reducing 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 relationship navigation.

“The flip side of our findings is that those who had increased 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. Therefore, improving the health and quality of our relationships is key to minimizing our risk of depression.

The study provides initial empirical evidence in support of the social signaling theory. But the researchers noted that the findings warrant further exploration and replication.

“There are still many other questions about who is most at risk of developing depression and under what circumstances,” Madison explained. “This research is important because we can then begin to identify the risk of depression and proactively take steps to reduce risk where possible. Additionally, identifying these underlying physiological mechanisms, such as inflammation, will ultimately help us treat depression more effectively.

“Importantly, these findings generalized across two samples with different interpersonal stressors (talking in front of strangers, marital conflict) and different follow-up times,” Madison added. “Furthermore, the results only applied to interpersonal stress and not to other forms of stress (such as work-related stress). Therefore, our results indicate the strength of the theory.

The study, “Frequent Interpersonal Stress and Inflammatory Reactivity Predict Increased Depressive Symptoms: Two Tests of the Social Signaling Theory of Depression,” was authored by Annelise A. Madison, Rebecca Andridge, M Rosie Shrout, Megan E. Renna, Jeanette M. Bennett, Lisa M. Jaremka, Christopher P. Fagundes, Martha A. Belury and William B. Malarkey, and Janice K. Kiecolt-Glaser.