GAITHERSBURG, Md. (WNEW) — Millions of people will turn their clocks back an hour on Sunday, but for some the extra hour of sleep gained is not worth the hours of daylight lost.

Doctors say a condition called Seasonal Affective Disorder (SAD) starts for many people around this time of year when there is less sunlight.

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“About 60-percent of the U.S. population is diagnosed each year,” said Dr. Lynnae Hamilton with Adventist Healthcare Behavioral Health and Wellness Services. “You may have a loss of interest in the things you used to really used to enjoy doing.”

Dr. Hamilton says SAD can be prevalent with college kids and tends to occur more in younger people. However, you can’t “outgrow” the disorder either.

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“You can have this type of disturbance that will start in the fall or winter and it can hang on with you until spring,” Dr. Hamilton said.

Symptoms of SAD include feeling depressed, weight gain, low energy and irritability. Those symptoms can last well into winter and, in some cases, spring.

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Exercise, light therapy and medication are all ways to treat SAD, doctors say.