Sleep, work, and happiness.

Read this article in the New York Times about how people sacrifice sleep in favor of work.  It links to this study that shows that higher wage rates reduce sleep time for men.  Given my previous posts about Gen X earnings being at peak during our 40s, I would suppose that we are also getting less sleep than ever!  No wonder we are more depressed and less happy.

So, since lack of sleep leads to worsened depression is it a vicious cycle?  Or just a chicken and egg problem?  Or a set of spurious correlations?