It's a counterintuitive idea, but depression could actually be a good thing. The Independent addresses the question by looking at studies and talking to experts and depression sufferers. Though not everyone agrees, a surprising number seem to think the answer is yes: Those who suffer depression and come out the other side have "seen the abyss" and end up stronger. Of course, experts are cautious in their phrasing: "Depression can end in suicide, so it is not to be taken lightly," says one.
However, she adds, "many people say it helps them evaluate what is important," and in that sense it can act as a wake-up call, causing people to make positive lifestyle changes. One Dutch study shows that after depression, respondents had improved ratings of psychological health and other indicators; another study shows that women with depression were more likely to live longer. Of course, notes one former sufferer, "Not everyone can feel any benefit from depression. ... But there are others for whom it has been a turning point."