The issue with poor sleep is actually poor slow wave sleep. This is the specific subtype of overall sleep that is reduced in depression, even when the individual sleeps too much.
Several studies have investigated the question, but a very recent one best illustrates the possible relationship between sleep and insulin/glucose control.
The study took "normal" non-diabetic subjects, and selectively reduced their slow wave sleep-- the deep sleep that is often found in naps-- but left the...

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