Healthy Mind

Seasonal affective disorder

Seasonal Affective Disorder (SAD) is a type of winter depression that affects an estimated half a million people every Winter between September and April, in particular during December, January and February. Experts believe SAD is related to a lack of daylight exposure, which explains why people feel well during spring and summer and only start experiencing problems when the days get shorter.

It is caused by a biochemical imbalance in the hypothalamus due to the shortening of daylight hours and the lack of sunlight in winter. For many people SAD is a seriously disabling illness, preventing them from functioning normally without continuous medical treatment. For others, it is a mild but debilitating condition causing discomfort but not severe suffering. We call this subsyndromal SAD or 'winter blues.'

The symptoms of SAD usually recur regularly each Winter, starting between September and November and continuing until March or April. A diagnosis can be made after three or more consecutive Winters of symptoms, which include a number of the following

SAD may begin at any age but the main age of onset is between 18 and 30 years. It occurs throughout the northern and southern hemispheres but is extremely rare in those living within 30 degrees of the Equator, where daylight hours are long, constant and extremely bright.

To treat SAD ensure exposure to plenty of daylight. Light boxes provide a regular dose of artificial light each day and help many people. Counselling, exercising and spending time outdoors can help. Boost mood with rest, relaxation, regular exercise and a healthy diet. Treatment with antidepressants or St John's wort may help to relieve symptoms.