Many of the emotional symptoms of stress can be triggered by changes in seasons. A person with seasonal affective disorder (SAD) sleeps too much and eats too much (thereby gaining weight) during the winter. Then the person begins to “wake up” in the spring and can even be slightly euphoric. In short, SAD has many of the features of hibernation —oversleeping and storing up high fat or carbohydrates for the cold winter. It’s “bear and squirrel” behavior in humans, which can be debilitating. Sometimes stress can mask SAD, or vice versa. SAD is a fairly recent diagnosis, first used in 1987.

SAD strikes people in their twenties and thirties, and is seen more in regions at higher latitudes. Living or working in areas that are light-deprived also can lead to SAD. For example, people who spend weeks or months at a time on submarines exhibit symptoms of SAD.

Light at the end of the tunnel is in sight for people with SAD—literally. If you’ve been diagnosed with SAD, you may be prescribed light. Often, the cure for SAD is to recreate the kind of light you’d naturally be exposed to on a nice summer’s day. Sitting under your chandelier won’t do. For this therapy to work, you need to sit in front of bright, full-spectrum fluorescent or incandescent lights for about 30 to 120 minutes. It’s not necessary to have sunlight or sun-like light. To protect your eyes, the lights are covered with a sheer material. You can get the light you need with a light box. Just do whatever you like in front of these lights. You’ll need to sit close—only about a foot and a half away. You need to keep your eyes open, so napping isn’t a good activity. If you prefer to sleep, there is an experimental device known as a dawn simulator, which can work while you sleep. Most people start to feel better in a few days of light treatments of just 30 minutes per day.

Even this treatment has some side effects. Mild headaches or eyestrain are not unusual, and sometimes mild mania (from the production of serotonin) may occur. If you’re taking a drug that makes you sensitive to bright light, you are not a good candidate for this therapy. See your doctor for information on purchasing a light box.

Bright-light therapy has also been shown to help depression that isn’t necessarily SAD but is related to sleep disorders involving circadian rhythm (the body’s natural sleep-wake cycle). In this case, light therapy during the day has been shown to help with sleep problems.