From: Annual variation in daily light exposure and circadian change of melatonin and cortisol concentrations at a northern latitude with large seasonal differences in photoperiod length
Time of the day
(hh:mm)
11:00
15:00
19:00
23:00
3:00
7:00
Cortisol concentration
Mean (pg/ml)
0.19
0.11
0.20
0.16
0.50
N = 15
SD (pg/ml)
0.28
0.13
0.45
0.31