That could potentially lead to more mutated cells that can trigger cancer. Studies in shift workers found that less melatonin may also lead to lower levels of important chemicals the body uses to repair DNA. In winter months when the days are shorter, melatonin levels may peak earlier or later in the day, which can lead to some of the mood changes linked to SAD. As more light creeps in during the morning, the levels of the hormone start dropping again. Normally, people produce more melatonin toward the evening, as the body gets ready for sleep. There is also intriguing evidence finding that people who work at night and don’t get exposed to daylight may produce less melatonin, a hormone that is dependent on light. People who consistently work night shifts, for example, tend to be heavier than people who don’t. That can have domino effects on nearly everything: how we break down energy from food, how strong our immune systems are and the vast array of brain chemicals and other substances that contribute to mood, weight, energy and more. Messing up the normal light and dark cycles by sleeping during the day and being awake at night, under artificial light, can disrupt the body’s metabolism. Studies of shift workers also support the possible role that exposure to sunlight has on mood. TIME Health Get the latest health and science news, plus: burning questions and expert tips. What's the Secret? The Science of Bouncing Back Do Cranky People Really Die Younger Than Pollyannas? This Is The Best Way to Overcome Fear of Missing Out The Healing Power of Nature The Mindful Revolution You Asked: Is Seasonal Affective Disorder Real? Here’s How Happy Americans Are Right Now Do Happy People Really Live Longer? Get Happy in Life It’s Official: Happiness Really Can Improve Health 6 Secrets to a Happier Life Why Having Lots of Feelings Is Good For Your Health These States Are the Happiest and Healthiest 9 Easy Ways to Get More Grateful 3 Science-Backed Ways to Relieve Pain and Stress The Secret to Happiness Is Helping Others See the Cities Where You Can Be Happier With Less Money These Are the Happiest and Healthiest Cities in America 14 Ways to Squeeze More Joy Out of Every Day Old People Are Happier Than People In Their 20s Being Happy Won’t Make You Live Longer Why Chasing Happiness Might Be Making You Miserable You Asked: Can Smiling A Lot Really Cause Wrinkles? Happy Thoughts: Here Are the Things Proven To Make You Happier Ancient Philosophers Reveal 4 Rituals That Will Make You Happier Norway Is Happiest Country in the World.

Staring at the sun spiritual