Why does sleep deprivation alleviate symptoms of depression?

Here's a link to an interesting article in the New York Times about depression and sleep that surprised me. A couple of months ago the neighbours upstairs had a new baby. He cries a lot, day and night, and you would think that the sleepless nights his crying causes could easily make anyone depressed. Indeed, postpartum depression can be remarkably common, affecting anything between 5-25% of new mothers in the first few months after giving birth. But if anything, according to this article by Terry Sejnowski, a renowned computational neurobiologist, an entire night without sleep can actually lift symptoms of depression in such afflicted women. Unfortunately, this is no miracle cure. You cannot escape the lack of concentration, irritability and memory loss inevitable after a night without sleep, and even the shortest nap can break the spell. Exactly how sleep deprivation alleviates symptoms of depression is still a still largely unknown, but one avenue of research scientists are currently exploring focuses on general sleep patterns with a particular focus on the rapid eye-movement (REM) stages of sleep. A link between REM sleep and depression has already been made: a common antidepressants blocks REM sleep and people with a genetic predisposition for entering REM sleep very early on in their sleep cycle are at a larger risk of becoming depressed. Thus, while staying awake for one night may not actually, at least not in a longer term, cure or even treat depression effectively, the alleviating effects of staying awake may give scientists an interesting direction for research into depression.