As one more piece of the puzzle, since you mentioned several times doing you best work at night and it being hard to get up in the morning, I can wonder how much of various stresses for many people may come from perhaps being a night owl in an early-morning lark business culture?

Also in one study, even just one night of missed sleep can lead to bipolar cycling in some people -- discussed by Matthew Walker in his book "Why We Sleep: Unlocking the Power of Sleep and Dreams".