If you live in an area characterized by lots of overcast, gloomy days in the winter months, you may be a victim of seasonal affective disorder, or SAD, a mood disorder associated with episodes of depression and related to seasonal variations of light. Symptoms of SAD include exhaustion and chronic sleepiness, the need to sleep nine or more hours a night, feelings of sadness, excessive eating and weight gain, and powerful carbohydrate cravings, especially for sugary and/or starchy foods. You might also have a difficult time concentrating. Often these symptoms emerge during the fall and winter months as the days grow shorter and darker, and light becomes an infrequent visitor. They then disappear as spring turns over a new leaf on the day and longer, brighter days herald the onset of summer, which invigorates people's zest for life again and squelches any signs of depression.

Because our internal clocks, rhythms, and regulators are heavily influenced by exposure to light, it's no surprise that one of the main causes of SAD is prolonged deprivation of adequate sunlight that our bodies need to stay on track. The hormones that affect mood, energy, and even food cravings can become imbalanced. Hence the ways to prevent and/or treat SAD include arranging for exposure to light every day (natural sunlight, or using light box therapy), staying active and maintaining routine physical exercise, and scheduling a mid-winter vacation where you go to a warm, sunny place.

SAD is a serious problem that requires the attention of a seasoned (no pun intended) professional.