Over at the Phineas Gage Fan Club, they've reviewed a recent research article (link unavailable) that looked at brain imaging differences between two groups: those that have had adequate sleep, and sleep-deprived individuals. Specifically, the researchers examined differences in amygdala functioning (a part of the brain involved in the regulation of emotion), as well as connectivity between the amygdala and the pre-frontal cortex (which is involved in the regulation of the amygdala). The research demonstrated more significant activity in the amygdala, and a corresponding decrease in regulation of the amygdala by the cortex. While this stuff can get extremely technical, the science is again pointing in the direction that getting a healthy amount of sleep on a regular basis is good for you in numerous ways, including in managing your moods. In layman's terms, "Sleep better=do/feel better, and do/feel better=sleep better." Each impacts the other positively.
As a side benefit to linking to this post, I was able to write the word amygdala. Can one ever get tired of that?