Social support and the demand-discretion model of job stress: Tests of additive and interactive effects in two samples

This article reports two studies which examine the role of social support in the context of the demand-discretion theory of job stress, with particular reference to additive versus interactive models. In Study I, data from a heterogeneous sample of health-care workers (N = 145) were analyzed using regression methods; after control for demographic factors, occupational group, and negative affectivity, job satisfaction was predicted by the main effect of support (p <.001), and by the demand × discretion interaction (p =.04). In contrast, somatic symptoms were predicted by a three-way demand × discretion × support interaction (p <.02), support mitigating the adverse effects of high strain as compared with low strain conditions. In Study II, longitudinal data from a homogeneous sample (N = 180) student teachers) were analyzed using a similar predictive model to examine Time 2 somatic symptoms, controlling for Time 1 levels. Again, the demand × discretion × support interaction was significant (p <.05); its form was closely similar to that found in Study I. These results are discussed in relation to the existing literature, with reference to theoretical and methodological issues.