Interesting. I believe in general inducing some stress every now and then is a good thing, so I can see that acute sleep deprivation occasionally might not be harmful. I've slept around 6 hours per night the last decade with no bad effects as far as I can tell. One thing to note about the article is that the author's correlation between depression and sleep is based on bipolar patients - people with unipolar depression normally sleep less when they are depressed.