An interesting article in the New York Times Magazine probes the link between the “core features” and “awful symptoms” of depression—such as “the inability of depressed subjects to experience pleasure or their lack of interest in food, sex and social interactions”—and “the capacity for intense focus.”
“[T[he mere presence of a challenging problem—even an abstract puzzle—induced a kind of attentive trance, which led to feelings of sadness. It doesn’t matter if we’re working on a mathematical equation or working through a broken heart: the anatomy of focus is inseparable from the anatomy of melancholy.”
“But is that closeness effective? Does the despondency help us solve anything? Andrews found a significant correlation between depressed affect and individual performance on the intelligence test, at least once the subjects were distracted from their pain: lower moods were associated with higher scores. ‘The results were clear,’ Andrews says. ‘Depressed affect made people think better.’ The challenge, of course, is persuading people to accept their misery, to embrace the tonic of despair. To say that depression has a purpose or that sadness makes us smarter says nothing about its awfulness.”

