WHITE-COLLAR WORK LOAD AND CORTISOL - DISRUPTION OF A CIRCADIAN-RHYTHM BY JOB STRESS

Perceived white collar work load was studied as a determinant of cortisol, an adrenal hormone with a pronounced circadian rhythm. Two hundred male NASA employees in administration, engineering and science, mean age 40, completed self-report questionnaires and gave blood samples. Respondents were grouped according to the time of day when their blood was sampled and were grouped into high, medium and low tertiles on an index of subjective quantitative work load. There was no main effect of work load on mean cortisol. There was a significant effect of level of work load on the relationship between time of day sampled and cortisol. High work load employees showed lower than normal morning cortisol values and did not show the expected decrease in cortisol from morning to afternoon. Low work load employees showed the expected circadian rhythm. We test two hypotheses which may further explain the results-(1) job satisfaction mediates the effect of work load on circadian rhythm and (2) personality traits produce self-selection into high work load environments-and discuss other interpretations. © 1979.