5 Things You Didn't Know About SAD and Sleep

by Kristina Brooks Editor

Seasonal Affective Disorder (SAD) is an illness that can cause mood swings, depression and severe fatigue. It is categorized as a mental illness similar to depression or bipolar disorder, and is estimated to affect 10 million Americans. Here are five ways in which sleep patterns can be affected by SAD.

You're not sleepy because it’s cold

SAD is commonly confused with the Winter Blues, which is a loss of energy due to falling temperatures, but can easily be cured with physical activity. SAD causes drowsiness due to the decreasing amount of daylight. The shorter, darker days of winter increase the body’s production of melatonin, which regulates sleep and depression.

SAD can cause insomnia or hypersomnia

People can develop SAD in either summer or winter seasons, but will display opposite symptoms. Those who experience SAD in the winter will have less energy and will sleep a lot more. Those who are affected by SAD in the summer will experience an energizing effect, which may cause insomnia.

Sunlight affects the sleep center of the brain

Experts agree that SAD is a disorder caused by the biological effects due to changing amounts of sunlight. Although not fully understood, some experts believe that the changes in sunlight trigger the hypothalamus. This is the center of the brain that controls mood, appetite and sleep, and affects sleep by regulating melatonin.

You won’t feel refreshed by sleeping more

SAD is believed to be caused in part by shifts to our circadian rhythm, which manages our body’s sleep-wake cycle throughout the day. As a result, excessive napping, going to bed or waking up at unusual hours, and restless sleeping, even for longer hours, will cause a person to feel groggy.

SAD is also caused by circannual rhythms

Changes in your sleep pattern from SAD may be caused by the same changes that signal hibernation in animals. Whereas circadian rhythms are daily cycles, circannual rhythms are yearly - triggered by changes in light levels, rain, and the position of the sun in the sky. These patterns explain why animals hunt and gather food in the spring and summer, then eat and hibernate in the winter.

Kristina Brooks
Meet Our Writer
Kristina Brooks

Kristina Brooks was a digital editor at HealthCentral with a background in animal biology, ecology, and health science. While studying broadcast journalism, she discovered the great need for health reporters that could translate research to the public. In her work, she hopes to use research to help consumers make smart decisions about their healthcare, and empower patients to stay confident and in charge of their chronic conditions. She helped launch HealthCentral's inaugural MythWeek.