If the post-holiday season has left you feeling low, the cause could be something other than overwork, overeating, or overexposure to CNN.

Daylight hours are short in January. That can leave people feeling less than joyful and longing for a break in a sunny climate. But you don't have to go to a tropical island to get well. Just get outside for a while during daylight hours, and do it every day. The light will make you feel better.

Inside your workplace or your home, you are exposed to light levels that are between 250 and 1,000 lux. Outside, the light level can reach 20,000 lux or more. Researchers aren't sure why, but people feel better when they're exposed to bright light for part of the day, especially during winter.

A study at the University of Helsinki shows that office workers who are exposed to bright light during dark winter months report more vitality and fewer symptoms of depression.

To put more light into your day, try squeezing in a 20-minute walk outdoors during your lunch hour. Or get outside to do something you enjoy before work or after work, whenever the light is brighter.

For some people, winter blues are more than a minor aggravation. Some people are afflicted with seasonal affective disorder (SAD). Here are some of the symptoms:

  • Depression that begins in winter or fall.
  • Lack of energy.
  • Decreased interest in work or other significant activities.
  • Increased appetite and weight gain.
  • Carbohydrate cravings.
  • Increased sleep but still accompanied by daytime sleepiness.
  • Social withdrawal.
  • Afternoon slumps with decreased energy and concentration.
  • Sluggish or lethargic movements.

See your doctor if you experience these symptoms. Don't try to treat yourself, because other illnesses can cause the same symptoms. Sunlight would be ineffective if your problem has a different physical or psychological cause.

If you have the symptoms of SAD, your doctor can recommend using a special light box for half an hour each day. It will make you feel better within a week. The light box can be used at home or at work if it fits in with your job.