Depression

If you think you have a life-long pattern of seasonal mood changes, you may have seasonal affective disorder. The depressed mood should be related to the season itself, rather than a reaction to periodic stress that occurs at the same time every year (like starting a new school year or an annual work commitment).

The winter doldrums are not rare, especially in areas of the country where winters are colder and longer. Seasonal affective disorder is found more in northern states than southern states. Throughout the world, it is more common farther from the equator. It is more common in women than men.

Experts believe that reductions in the amount of light are an important factor in bringing on the mood changes. Biological rhythms are synchronized with periods of light and dark, and mood regulation is linked to these rhythms in the brain.

Colder weather that keeps people inside and reduces their activity level may also be a factor. Reduction in exercise levels can depress a person's mood. Also, when people stay inside, they take less advantage of whatever bright sunlight is available.

There may be a connection between seasonal affective disorder and bipolar disorder. Scientists think so, because the depression in seasonal affective disorder (which causes increased sleep and appetite, along with low energy and weight gain) is similar to the depression seen in bipolar disorder. In fact, many people with a seasonal mood pattern do have bipolar disorder. People with bipolar disorder sometimes have manic or hypomanic episodes in a seasonal pattern, too -- those episodes occur more frequently in summer. This pattern may also relate to biological rhythms and the amount of light.

Standard treatments for depression are effective for this form of seasonal affective disorder.

Light therapy is also sometimes recommended, particularly in the winter time. Bright light may "reset" biological clocks and therefore may help the brain regulate mood.