CHARLOTTE, N.C. -- Thursday was the darkest day of the year both literally and, for many, mentally.

It was the 2017 winter solstice, which is known to trigger or worsen seasonal depression in millions of Americans.

“People experience a sense of sadness that's overwhelming,” one doctor explained. “It's not just, 'I wish the winter would go away I can't wait for spring,' sometimes it's so impactful that people can't get out of bed.”

“It could lead to suicidal thoughts during these kinds of episodes which is why you do not want to ignore this type of depression.”

It's called seasonal affective disorder, or SAD, a type of depression that usually comes on during the winter and vanishes by spring.

You might know it as the "winter blues." Experts say it has to do with the reduction of sunlight.

Now, medical research suggests tricking our bodies could be the solution.

“A lot of people don't even know that they can make changes in the way they feel with light," said Carol Calvert, a light therapy expert based in Charlotte.

“You want to be in light more than not," she said.

You can buy light therapy lamps online, Calvert even invented her own. The idea is that the bulbs make your body think you're standing out in the sunshine.

And you don't need to drop a fortune. You can pick up the so-called "daylight" bulbs for a few dollars.

“Big box stores will not tell you that this is a wellness bulb but it is,” Calvert said. “This bulb will change the way you feel about life, period.”

She suggests installing daylight bulbs around your house and making it a point to go outside.

“Everyone, get out and spend time in the sun,” she said.

To learn more about seasonal affective disorder, including symptoms, click here.