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Biology Articles » Chronobiology » The circadian basis of winter
depression » Results  - The circadian basis of winter depression
Phase-Shifting Effects of Melatonin Were Sufficient to Test the
PSH. PM melatonin caused a 0.89-h phase advance in the clock
timeof the DLMO (t = 7.61, df = 21, P < 0.001) and a 0.69-h
increasein PAD (advance in the DLMO with respect to midsleep: t
= 4.66,df = 21, P < 0.001). (After PM-melatonin treatment,
meanDLMO clock time was 20:18 ± 0:14.) AM melatonin did
notsignificantly delay the DLMO (0.18 h) or decrease PAD
(0.01h). Placebo treatment was associated with nonsignificant
trends,an advance in the DLMO and an increase in PAD of both
0.17 h(t = 1.71, df = 23, P = 0.10; and t = 1.76, df = 23, P =
0.09,respectively), consistent with the photoperiod that
lengthenedthroughout the study. Nevertheless, because AM
melatonin andplacebo treatments did not produce statistically
significantchanges in circadian phase, the