The nuclear winter theory also remains controversial, with some scientists saying the predicted effects have been exaggerated.

核冬天理论也受到了质疑，有些科学家认为预测的结果被夸大了。

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One theory about Sad is that sufferers do not get enough light in winter to halt melatonin production, and this disturbs their sleep and appetite.

有关Sad的某一理论认为，患者在冬季未能得到足够的光照从而停止褪黑激素的分泌，这扰乱了他们的睡眠和食欲。

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Another theory is that it is easier for companies to deal with promotions after the winter or summer holidays。

另一种推测是，在寒暑假之后，公司处理升职问题会更容易。

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The theory behind outdoor napping is that children exposed to fresh air, whether in summer or the depths of winter, are less likely to catch coughs and colds - and that spending a whole day in one room with 30 other children does them no good at all.

BBC: The babies who nap in sub-zero temperatures