Shortly after the market's big drop in September 2008, this phenomenon — photos of stunned and sad people shuffling through their day on the trading floor — became the perfect fodder for Tumblr.

There’s a long tradition of depressing sci-fi in films like “Moon,” “Interstellar” and “2001: A Space Odyssey” ...

But in some cases, those changes in mood, sleep and appetite can be signs of something more serious: a form of depression known as seasonal affective disorder, or SAD. "It's normal for people to ...