Causes of seasonal affective disorder

The causes of Seasonal Affective Disorder are not fully understood. Research indicates the causes are similar to those of depression. The cause is also often linked to the reduced exposure to sunlight, commonly experienced during the winter months. Research has proven that sunlight can affect some of the brain’s chemicals and hormones (melatonin, serotonin and circadian rhythm) – but the effect is unclear.  

You are considered more likely to develop SAD if you have a relative with SAD or another type of depression. SAD is more common in women.