When you hear "January," do you think of days cut short, clouds, and gloomy skies? Do you miss the excitement of the recent holidays and instead feel a little down, with flagging energy? Or perhaps this time of year, you kick yourself for having a hard time completing simple daily tasks. These could be signs of Seasonal Affective Disorder, or SAD for short, and it's much more common than you might realize.

What causes SAD?

The absence of natural light because of winter's shorter daylight hours is the number one reason for the blue feeling that most characterizes SAD. Cold, cloudy, wet weather makes exercising and staying outdoors during the day more difficult. Staying indoors equals even less exposure to natural light, which can negatively affect the body's production of the neurotransmitter serotonin. Low levels of serotonin trigger a depressed feeling that's hard to shake.

Many people that I see in my office complain of the "winter blahs" in varying degrees and mistakenly feel alone in their condition. I explain that this is a common pattern that is shared by many who are sensitive to the changes of the seasons, starting as early as October and November. SAD sufferers report that getting out of bed in the morning, feeling energized, and even socializing normally all are more challenging in the fall and winter seasons than in the spring and summer months.

If that sounds familiar, here are some things you can do remain positive and keep your batteries charged this winter.

Brighten your physical environment. Natural sunlight helps most, so let it in. Roll away dark shades, sit next to a window in your office, and make a point of getting outside for breaks whenever possible.

Move around. Join a gym, get an exercise CD, or just get up and stretch. Staying sedentary only contributes to that lethargic, heavy feeling, so incorporating walks outside during the day would make difference and help to lift your mood.

Invest in a phototherapy lightbox. This is a small investment with big returns. It generally only takes 30 minutes each morning to get positive results from a phototherapy device. What's more, some insurance plans will even help with the cost of a lightbox if your doctor indicates you'd benefit from it.

Stay connected. Make more of an effort than usual to connect with friends, family, and colleagues.

Utilize stress management techniques that are available. These include yoga, meditation, acupuncture, massage, guided imagery, support from a holistic practitioner, and/or even a professional evaluation for depression if necessary.

Avoid fatty, sugary, or heavy foods. While comfort foods might make you feel safe, relaxed, and uplifted for a short while, the lethargy and weight gain that can crop up in the long run have the opposite effect.

Try nutritional supplements. Vitamin D ("the sunshine vitamin") and omega fish oils are effective in combating feelings of depression.

Plan a vacation. This is my favorite! If you sing the winter blues, make a point of visiting a warmer, sunnier climate.

Change your mindset. Don't get locked into "This is just the way I always feel in January" self-talk. That's defeating. At the same time, don't feel like you must reinvent every detail of your life because it's a new year, either. That can only lead you to feel overwhelmed and intimidated. Instead, make a list of activities that you'll look forward to enjoying. View the new year not only as a fresh start but also as a door leading to new opportunities. And remind yourself that this door is built on the firm foundation of the happiness and success you enjoyed in preceding years.

SAD is common, but you don't have to be a victim. You can develop control over it. Now that you know the facts, it's time to act. Identify at least one thing you can do today to move out of the blahs. You can shake off the winter slump.