People who experience high inflammatory reactivity to socially stressful situations are more likely to develop depressive symptoms, according to a new study published in Psychological Science. The findings provide new insights into how interpersonal stress and inflammatory responses are related to mental illness.
“We set out to discover why psychological stress, and particularly interpersonal stress, triggers depression in some people but not others,” explained study author Annelise Madison, a PhD candidate in clinical psychology at The Ohio State University.
“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 empirically tested, so we did so among one sample of breast cancer survivors and other 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 collected approximately 90 and 300 minutes after the conflict. The researchers found that those who reported more frequent interpersonal conflict had heightened depressive symptoms approximately one month later, but only if they had greater inflammatory reactivity to the marital conflict.
In the second study, 79 breast cancer survivors provided a blood sample before completing the Trier Social Stress Test, an experimentally-verified stress-inducing scenario consisting of a speech and a mental-arithmetic task. The participants then had their blood drawn again 45 and 120 minutes after the stress test. The researchers found that participants who felt lonelier and less socially supported tended to have heightened depressive symptoms one year later, and this was especially 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,” Madison told PsyPost. “These findings suggest that we can take steps to reduce depression risk by 1) lower our physical reactivity to stress via strategies such as regularly engagement in mindfulness meditation; or 2) reduce our exposure to interpersonal stress through more skillful navigation of relationships.”
“The flipside of our 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. Therefore, improving the health and quality of our relationships is key for minimizing our risk of depression.”
The study provides some initial empirical evidence in support of the social-signal-transduction theory. But the researchers noted that the findings warrant further exploration and replication.
“There are still many more questions concerning who is most at risk for developing depression and under what circumstances,” Madison explained. “This research is important because then we can start identifying depression risk 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.”
“Importantly, these results generalized across two samples with different interpersonal stressors (a speech in front of strangers, a marital conflict) and different time frames for follow-up,” Madison added. “Also, the findings only held true for interpersonal stress and not other forms of stress (like work-related stress). Therefore, our findings point to the theory’s soundness.”
The study, “Frequent Interpersonal Stress and Inflammatory Reactivity Predict Depressive-Symptom Increases: Two Tests of the Social-Signal-Transduction 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.