Is it seasonal depression or just the winter blues?
Even if you're not clinically depressed, a little light can counter sleepiness, low energy, and carbohydrate cravings.
The dark nights are longer these days, but they don't have to be dark nights of the soul. Although only 5% to 10% of the population has outright seasonal affective disorder (SAD)—marked by sadness, loss of interest in regular activities, exhaustion, and weight gain—about 25% of people living in the middle and northern regions of the United States get the winter doldrums—milder changes in mood, alertness, energy, and appetite. SAD requires professional treatment, but the winter doldrums can be more easily banished.
The role of light
Light affects the body's supply of melatonin and serotonin. Both are neurotransmitters—chemicals that carry messages throughout the nervous system. When the days are shorter, more melatonin, which helps to induce sleep, is produced. and melatonin levels remain higher longer into the morning. As a result, you may feel sleepier as you start the day. In contrast, production of serotonin, which elevates mood and contributes to satiety, is triggered by light, so less of it is produced during the winter. You may feel less cheerful and have more food cravings, particularly for carbohydrates.