SAD: One Cause of the Holiday Blues

Recurrent Winter Depression Could Be a Sign of Seasonal Affective Disorder

The blues are an unfortunate part of the holiday season for many people. Some individuals suffer from depression more acutely during this time of year due to the pain of lost loved ones or from the stress and pressure that Christmas can bring. Others, however, can find no obvious cause for their low mood, or for the reason that their mood seems to lift as soon as the weather warms and the snow melts away.

Individuals who experience these recurrent depressive episodes often show a seasonal pattern, commonly known as seasonal affective disorder, or SAD. Individuals with this subtype of mood disorder appear to be responsive to the total quantity of available light in the environment, with a majority of them becoming depressed in the fall and winter when less natural sunlight is available. Features of SAD include fatigue, excessive sleep, craving for carbohydrates, and weight gain, and individuals with this disorder often show clear disturbances in their circadian cycles, with weaker 24-hour patterns than normal individuals.

Although the cause of seasonal affective disorder is not clear, one possibility is that seasonal changes in light may alter the body's underlying biological rhythms that regulate such processes as body temperature and sleep-wake cycles. Another possibility is that some parts of the central nervous system may have deficiencies in transmission of the mood-regulating neurotransmitter, serotonin, during winter months.

SAD develops in women more often than men, and nearly half of those affected report that episodes began during childhood or adolescence. Prevalence rates for seasonal affective disorder suggest that winter SAD is more common in individuals living at higher latitudes (northern climates) and in younger people. Seasonal affective disorder can, and sometimes does, cause depression during the summer months as well.