An interesting article in the Guardian by psychiatrist Paul Keedwell argues that depression can have some benefits:
The truth is that short-term pain can lead to longer-term gain. A
recently published follow-up study of depression in Holland – the
Netherlands Mental Health Survey and Incidence Study (Nemesis) – used a
sample of 165 people with a major depressive episode, and provides some
preliminary scientific evidence to suggest that depression is indeed
helpful in the longer term. Researchers who were looking for evidence
to suggest that depression leaves people chronically disabled were
surprised to discover the opposite.
His new book, How Sadness Survived: The Evolutionary Basis of Depression, looks fascinating – at the time of writing, the reviews that I’ve seen have all been five-star!