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Table 4 Means and standard deviations for seasonal and annual mean melatonin concentration at the six time points during the day

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

Season   Time point
(hh:mm)
   11:00 15:00 19:00 23:00 3:00 7:00
Winter Mean (pg/ml) 3.12 2.30 1.94 4.52 6.74 3.82
  SD (pg/ml) 4.59 2.51 1.47 2.95 5.15 1.91
Spring Mean (pg/ml) 2.20 2.06 1.66 3.89 5.44 2.30
  SD (pg/ml) 1.56 1.76 1.06 2.04 3.84 1.53
Summer Mean (pg/ml) 2.09 1.95 1.81 3.15 5.97 2.32
  SD (pg/ml) 1.74 1.31 1.62 2.05 3.68 1.53
Autumn Mean (pg/ml) 2.12 1.91 1.88 3.03 5.24 2.47
  SD (pg/ml) 1.54 1.51 1.64 1.68 3.83 1.21
Annual average Mean (pg/ml) 2.39 2.03 1.84 3.61 5.73 2.69
  SD (pg/ml) 1.47 1.38 1.50 3.34 5.08 2.58