Season Affective Disorder (SAD)

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Some people are vulnerable to a type of depression that follows a seasonal pattern. For them, the shortening days of late autumn are the beginning of a type of clinical depression that can last until spring. This condition is called “Seasonal Affective Disorder,” or SAD.

SAD is thought to relate to seasonal variations in light. A “biological internal clock” in the brain regulates our circadian (daily) rhythms. This biological clock responds to changes in season, partly because of the differences in the length of the day. For many thousands of years, the cycle of human life revolved around the daily cycle of light and dark. We were alert when the sun shone; we slept when our world was in darkness. The relatively recent introduction of electricity has relieved us of the need to be active mostly in the daylight hours. But our biological clocks may still be telling our bodies to sleep as the days shorten. This puts us out of step with our daily schedules, which no longer change according to the seasons. Other research shows that neurotransmitters, chemical messengers in the brain that help regulate sleep, mood, and appetite, may be disturbed in SAD.

What are the Symptoms?
SAD can be difficult to diagnose. Generally, symptoms that recur for at least 2 consecutive winters and may include:
change in appetite, in particular a craving for sweet or starchy foods

Research in Ontario suggests that between 2% and 3% of the general population may have SAD Another 15% have a less severe experience described as the “winter blues.” SAD tends to begin in people over the age of 20 and is more common in women than in men. Recent studies suggest that SAD is more common in northern countries, where the winter day is shorter. Deprivation from natural sources of light is also of particular concern for shift workers and urban dwellers who may experience reduced levels of exposure to daylight in their work environments. People with SAD find that spending time in a southerly location brings them relief from their symptoms.