Are stress-induced immunological changes mediated by mood? A closer look at how both desirable and undesirable daily events influence sIgA antibody

This investigation tested a three-path model of mood as a mediator of the relation between stress and immunity. Seventy-two married men completed end-of-day diaries in which they rated their mood for that day and the desirability of the day's events for 12 weeks. Events were coded as either desirable (nonstressful) or undesirable (stressful) in nature. Immunological functioning was assessed by secretory immunoglobulin-A (sIgA) antibody response to an oral antigen. Regression analyses indicated that negative mood partially mediated the immunological response to both undesirable and desirable events. Undesirable events lowered antibody level primarily by increasing negative mood; desirable events increased antibody levels by decreasing negative mood. Evidence for mediation by positive mood beyond that found for negative mood was weak.