They have learned that there are five stages of sleep.

他们认识到睡眠分为五个阶段。

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It's known that levels of growth hormone rise during certain stages of sleep.

在睡眠进行的一定阶段的时候，生长类的激素就会上升。

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Then they explored the various aspects of mood and their relationship to the various stages of sleep and dreaming.

接着，他们研究了情绪的不同方面和它们的睡眠和梦不同阶段的关系。

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Many of us tolerate this anxiety and exhaustion every day of our lives and never get the chance to repair our bodies with the deepest stages of sleep.

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While the science is in the early stages, one hypothesis suggests that by promoting feelings of safety and security, shared sleep in healthy relationships may lower levels of cortisol, a stress hormone.

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