Winter got you feeling down? Watch this - Kelly Rohan

Every year, people leave their doctor's office with an unusual prescription.

Instead of traditional treatments like a pill, shot, or cream, they’re sent home with a recommendation for light— or more specifically, light therapy.

To understand how this works, let’s step out of the office and into this valley.

Here, as winter approaches, shorter days spark a cascade of changes within the brains of its inhabitants.

As a result, groundhogs retreat to their burrows for hibernation.

Weasels’ coats turn from brown to white, and birds cease their singing.

And scientists are finding that seasonal behavioral changes similarly happen for some humans.

Around 1% of people experience seasonal affective disorder, or SAD, a mood disorder marked by episodes of depression that recur at certain times of the year.