Causes of Seasonal Affective Disorder

Did you know that as many as 1 in 20 people suffer from seasonal affective disorder (SAD)? It is thought that the lack of sunlight disrupts the circadian rhythms, the internal biological clock. Geographical differences in the diagnosis of SAD supports the theory that lack of light is the culprit. SAD becomes more common the further you get from the equator. Research suggests that while about 1% of people in Florida get SAD, it´s closer to 10% in New Hampshire. Many more people have milder versions of SAD, meaning that they experience some symptoms, but not enough for a formal diagnosis.