If you're sad just because it's winter... The problem may be due to a mutant gene in the eye.
Millions of Americans suffer from what's called seasonal affective disorder. A kind of winter-time depression that's sometimes treated by putting them in front of bright lights.
Now scientists at the University of Virginia have discovered a genetic abnormality in the eye. They say it makes people less sensitive to light... So that everything in the daylight-shortened winter appears even more drab than usual.