It is common to eat and sleep more during the winter months. People feel deflated when dark mornings and short days signal the onset of the season. For some, these feelings become severe and cause considerable disruption to daily life.
Seasonal Affective Disorder (known as SAD) is not a psychosomatic or imaginary illness. It is a form of clinical depression, which can seriously disable sufferers.
People with mild symptoms benefit from self-help activities such as exercise and exposure to light, whereas those with severe SAD may also require medical assistance in the form of antidepressants and counselling.
SAD affects 2 million people in the UK each year.
Approximately 2% of people in Northern Europe suffer from the condition. 10% cope with milder symptoms, known as sub-syndromal SAD, or winter blues.
Other areas that experience less-dark winters have a lower incidence of SAD. In Florida, less than 1% of the population suffer from it.
Meanwhile in Canada, as many of 10% of people experience some form of winter depression.
More women than men suffer from the condition, and younger people are also vulnerable.