Socioeconomic status, perceived control, diurnal cortisol, and physical symptoms: A moderated mediation model.

Social class is a robust predictor of health, with risk for disease and mortality increasing towards the lower end of the socioeconomic (SES) spectrum. While certain psychological characteristics, such as high sense of control, can protect low-SES individuals from adverse health outcomes, very few studies have investigated the biological mechanisms underlying these relationships. In this study, we tested whether sense of control mitigated the associations between SES and cortisol activity, and SES and physical health in daily life (i.e., number and severity of physical symptoms). Next, we tested whether individual differences in cortisol secretion would act as a mechanism by which SES and perceived control influenced physical health. In a large national sample from the Midlife in the United States (MIDUS) survey, we found that SES interacted with perceived control in predicting morning cortisol levels, cortisol slopes, number of physical symptoms, and severity of physical symptoms. Specifically, SES disparities in these health outcomes were more pronounced among individuals reporting low levels of perceived control than among individuals endorsing high levels of perceived control. Further, we found that a flatter cortisol slope mediated the link between lower SES and greater number and severity of physical symptoms for those individuals who reported lower levels of perceived control, but not for individuals reporting higher levels of perceived control. These findings suggest that perception of greater control may act as a buffer against the effect of low SES on health-related physiological processes.