Winter sunlight can be in short supply, but it's worth seeking out.

RODALE NEWS, LENOX, MA—Are you getting enough light? If you’re like most of us, you may not be. Even without record-setting blizzards like we've seen this winter, more and more Americans are spending less and less time outdoors. As we spend more time indoors, we are becoming increasingly deprived of the bright-sunlight exposure that is essential to our health and well-being. The resulting light deficiency can cause fatigue, irritability, depression, carbohydrate craving, sleep problems, and weight gain. Getting 30 minutes of sunlight exposure a day can dramatically improve these symptoms. Exposure to sunlight immediately boosts levels of neurotransmitters that produce a feeling of relaxed well-being. In addition, long-term exposure to sunlight raises levels of vitamin D, an essential nutrient that most Americans are deficient in.

THE DETAILS: If you live in a northern state, by this time of year you may be experiencing significant light deprivation, thanks to both shorter days and more time spent indoors. Most people in northern states feel more irritable and sluggish in the winter, and studies also show that people who live in sunny climates tend to feel happier than people in darker environments. In fact, a recent survey of 1.3 million Americans found that those who live in the sunniest U.S. states tend to report the highest levels of happiness. The seven happiest states in the 50-state survey were all in the Sun Belt: Louisiana, Hawaii, Florida, Tennessee, Arizona, South Carolina, and Mississippi.

Although light deprivation is more prevalent in the winter, it does occur year round. People who suffer from Seasonal Affective Disorder, or winter depression, often experience symptoms of depression at other times of year if they don’t get enough light, and they benefit dramatically from high-intensity light exposure. People with nonseasonal depression, and those suffering a variety of other conditions, have also been found to improve with exposure to high-intensity light. Light therapy can be helpful for PMS, depression during pregnancy, bulimia, and insomnia.

How does it work? Bright light absorbed through the eyes stimulates production of serotonin, the same neurotransmitter that's boosted by the type of antidepressant medication called selective serotonin reuptake inhibitors (SSRIs). The effect can be quite remarkable. For treating depression, bright light works faster—usually within a week—with fewer side effects than medication.

Read on for advice about bringing more healthy-sunlight exposure into your life.