The Effects of Red and Blue Lights on Circadian Variations in Cortisol, Alpha Amylase, and Melatonin

Figure 1

Study protocol. Seven equally spaced baseline measurements were always taken after three hours in the dark (open arrows), except for the first baseline measurement that was taken after one hour in the dark. Subjects were assigned to one of three sessions (red, blue, and dark) corresponding to one of the three lighting conditions they would experience during that session (R, B, and D). Except for the last one, lighting condition measurements were taken one hour after and three hours before each baseline measurements.