About one in four people are susceptible to the winter doldrums, marked by fatigue and food cravings caused by biological changes. The more severe seasonal affective disorder, or SAD, affects 11 million Americans with more serious signs of depression (“Beating Winter’s Woes,” WebMD).
Both conditions are caused by winter’s shorter days, which disrupt our circadian rhythm, or internal body clock. How severely each individual is affected is based on a combination of factors—geography, genetics and individual brain chemistry. “With SAD, the lack of sunlight causes the brain to work overtime producing melatonin, the hormone that regulates your body clock and sleep patterns and which has been linked to depression,” WebMD reports. “The farther north from the equator you live, the greater the risk you’ll have some degree of winter depression.” For example, only about 1 percent of Florida residents suffer from wintertime blues compared to about half of those living in uppermost parts of the U.S. or in southern Canada. Read more