Physical effects of daily stressors are psychologically mediated, heterogeneous, and bidirectional.

Prior research shows that daily stressors lead to greater psychological distress. A separate body of research links daily stressors to physical symptoms such as backaches and stomach problems. We integrate these literatures by positing an interconnected causal system, whereby stressors lead to psychological distress which, in turn, leads to physical symptoms. Our integrated approach also includes causal effects in the opposing directions: Psychological distress can increase physical symptoms and physical symptoms can increase psychological distress. Put simply, causal effects are bidirectional. This finding illuminates the concept of feedback loops, which have never been investigated in the stress literature until now. We find that reverberating feedback between stressors and distress equilibrates after just one and a half loops and that feedback between stressors and physical symptoms does not actually reach a full loop. Because of this, feedback loops have only minor consequences for physical symptoms by the end of the day. Finally, we discuss the aforementioned phenomena with between-person differences at the forefront, showing how some people are as much as four times as reactive as the average person, some people are not reactive at all, and other people are reactive in reverse directions (e.g., distress leads to fewer physical symptoms). We empirically support these claims using daily diary data from three separate studies that together represent diverse ages, geographic regions, relationship statuses, and racial identities. Once established, we consider the implications of our integrated causal feedback system in relation to existing knowledge and highlight critical areas for future study. (PsycInfo Database Record (c) 2021 APA, all rights reserved).