The symptoms of SAD are similar to those of 'winter blues' (e.g. tiredness, lack of energy, overeating, low moods and social withdrawal) but SAD is much more severe, often seriously affecting people's performance at work, their home life and relationships. The cause of SAD is unclear but short, dark days are the trigger. They prolong the production of melatonin, normally only released at night to help us sleep. Another factor is thought to be low serotonin levels (a feature of depression) which improve significantly in the summer and with light therapy. Indeed, many SAD sufferers have found that bright lights can make a real difference to their life.
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