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Although evidence suggests that loneliness may increase risk for health problems, the mechanisms responsible are not well understood. Immune dysregulation is one potential pathway: Elevated proinflammatory cytokines such as interleukin-6 (IL-6) increase risk for health problems. In our first study (N = 134), lonelier healthy adults exposed to acute stress exhibited greater synthesis of tumor necrosis factor-alpha (TNF-α) and IL-6 by peripheral blood mononuclear cells (PBMCs) stimulated with lipopolysaccharide (LPS) than their less lonely counterparts. Similarly, in the second study (N = 144), lonelier posttreatment breast-cancer survivors exposed to acute stress exhibited greater synthesis of IL-6 and interleukin-1 beta (IL-1β) by LPS-stimulated PBMCs than their counterparts who felt more socially connected. However, loneliness was unrelated to TNF-α in Study 2, although the result was in the expected direction. Thus, two different populations demonstrated that lonelier participants had more stimulated cytokine production in response to stress than less lonely participants, which reflects a proinflammatory phenotype. These data provide a glimpse into the pathways through which loneliness may affect health. [ABSTRACT FROM PUBLISHER]

The death of a spouse is associated with maladaptive immune alterations; grief severity may exacerbate this link. We investigated whether high grief symptoms were associated with an amplified inflammatory response to subsequent stress among 111 recently bereaved older adults. Participants completed a standardized psychological stressor and underwent a blood draw before, 45 min after, and 2 hr after the stressor. Those experiencing high grief symptoms (i.e., scoring > 25 on the Inventory of Complicated Grief) experienced a 45% increase in interleukin-6 (IL-6; a proinflammatory cytokine) per hour, whereas those experiencing low grief symptoms demonstrated a 26% increase. In other words, high grief was related to a 19% increase in IL-6 per hour relative to low grief. The grief levels of recently bereaved people were associated with the rate of change in IL-6 following a subsequent stressor, above and beyond depressive symptoms. This is the first study to demonstrate that high grief symptoms promote inflammation following acute stress. [ABSTRACT FROM AUTHOR]

The social-signal-transduction theory of depression asserts that people who experience ongoing interpersonal stressors and mount a greater inflammatory response to social stress are at higher risk for depression. The current study tested this theory in two adult samples. In Study 1, physically healthy adults (N = 76) who reported more frequent interpersonal tension had heightened depressive symptoms at Visit 2, but only if they had greater inflammatory reactivity to a marital conflict at Visit 1. Similarly, in Study 2, depressive symptoms increased among lonelier and less socially supported breast-cancer survivors (N = 79). This effect was most pronounced among participants with higher inflammatory reactivity to a social-evaluative stressor at Visit 1. In both studies, noninterpersonal stress did not interact with inflammatory reactivity to predict later depressive symptoms. [ABSTRACT FROM AUTHOR]