Q. Starting in January each year, I get very depressed. I think I may have a low-level depression, but I deal with it effectively other times. In the winter, however, I don’t want to go to work, do things with friends or get out of bed. Why does this keep happening and what can I do about it?

Approximately 15 percent of depressed people report that their depression levels increase during the fall, grow worse during the winter and recede as spring approaches. This calendar-linked pattern of depression is referred to as Seasonal Affective Disorder or S.A.D. You have probably noticed that it happens about the same time each year. Many people link the start of their increased depression to the end of daylight saving time.

According to the Mayo Clinic website, there are several symptoms that are specific to S.A.D. or “winter depression.” These include:

• Unusual irritability

• Low energy or a feeling of being constantly tired

• Problems getting along with others

• Hypersensitivity to rejection

• Heavy feelings in the arms and legs

• Over-sleeping

• Appetite changes such as craving more carbohydrates than usual

• Weight gain

Although the specific causes of S.A.D. are unknown, there are several possible contributing factors:

• One’s biological clock, or circadian rhythms, don’t adjust properly to the decreased level of sunlight.

• Reduced sun exposure can decrease levels of serotonin, a brain chemical, which may lead to an increase in depression.

• Seasonal changes can disrupt the body’s melatonin levels, which can cause one to need more sleep than usual.

There are several factors that increase the likelihood of developing S.A.D. Younger females are more likely to have seasonal disruptions. However, when males have S.A.D., the symptoms are often more severe. If one already has a depressive disorder or bipolar disorder, the winter months often exacerbate the severity of the condition.

Even where one lives may determine the likelihood of developing S.A.D. The further one lives from the equator heightens depression in those who are susceptible, since the amount of winter sunlight is decreased. Notice that many people begin to feel down when there are weeks of cloudy or rainy days.

Since you are likely experiencing S.A.D., it’s very important that you take extra care of your physical and emotional health during these months. First, practice good sleep habits, eat healthy foods and exercise as often as possible. Avoid alcohol and recreational drugs since they can worsen your depression. Second, get involved in pleasurable activities during shorter days. Don’t stay home, overeat or watch too much television. You will only become more depressed.

Many people with S.A.D. have been helped by “light box therapy,” which uses a special lamp that mimics sunlight. If you get a light box, take about 30 minutes in the early morning to sit a couple of feet away from it. This will mimic sunrise, and has been a very effective tool in alleviating depressive symptoms. Before starting this therapy, be certain that you are not taking a medication that makes you sensitive to light and have an eye examination by your ophthalmologist.

If your condition worsens or you feel suicidal, please contact a mental health professional immediately. There are also medications that can help you withstand the winter months with fewer depressive episodes.

— Nancy Ryburn holds a doctorate degree in psychology from Yeshiva University in New York City. She teaches psychology at Southeast Arkansas College and maintains a private practice.