Figure 2

Normalized melatonin concentrations for Experiment 1. Mean ± SEM melatonin concentrations for all subjects in the first study. As shown on the far left, the mean melatonin concentrations on night 2 (after light exposure) were significantly lower than on night 1 (dark night); mean suppression after 60-minute light exposure was 46%. The melatonin concentrations on night 2 were significantly lower than the comparable concentrations on night 1 while subjects were awake (mean suppression after 60-minute light exposure was 36%), during non-REM sleep (mean suppression 45%), and REM sleep (mean suppression after 60-minute light exposure was 56%).