Analysis of salivary cortisol levels to determine the association between depression level and differences in circadian rhythms of shift‐working nurses

SG nurses presented significantly increased salivary cortisol levels early in the morning during night shifts, showing a phase deviation in the circadian rhythm. Because subjective fatigue levels did not differ with time, SG nurses should understand and deal with physical changes in the early morning. This approach may reduce medical accidents and malpractice in the early morning.