Social Support at Work Carries Weight: Relations Between Social Support, Employees' Diurnal Cortisol Patterns, and Body Mass Index

Despite the preponderance of evidence documenting the benefits of workplace social support for employees, the link between social support and employees' physiological functioning and physical health outcomes has received relatively less research attention. In particular, diurnal cortisol patterns and body mass index (BMI) are key indicators of physiological functioning and physical health, respectively, that can be used to illuminate how social support influences employee health. However, existing applied psychology research has yet to examine the dynamic nature of diurnal cortisol secretion and its long-term effect on BMI change. Further, research linking social support and cortisol has produced conflicting findings. To address these critical gaps, we draw from Heaphy and Dutton's (2008) theory of positive social interactions at work and the allostatic load model (Sterling & Eyer, 1988) to link supervisor and coworker support at work to employees' diurnal cortisol pattern and change in BMI. We tested our hypotheses using growth modeling on a sample of Japanese employees with multi-wave data spanning across 6 years. We found support for our hypotheses regarding supervisor support but not coworker support, as cortisol exhibited a diurnal pattern, and higher levels of supervisor support were associated with more pronounced, healthier diurnal cortisol patterns, with a steeper decline from morning to evening, which were further associated with smaller BMI increases 4 years later. Overall, our findings suggest social support at work, especially supervisor support, can have far-reaching effects on employees' physical health. The implications of these findings for applied psychology research and practice are discussed.