This paper begins with a description and definition of the mood disorder known as
seasonal affective disorder (SAD), explaining
that it is a real and serious clinical depression different from the winter blues or winter 'blahs' that many people commonly suffer from during the winter months. The paper examines research on the
disorder and discusses its possible causes, the relationship that decreased levels of
melatonin and seratonin have regarding the occurrence of SAD, symptoms of SAD and the three main methods for treating the disorder. Table of Contents Introduction What is SAD? Effect of Melatonin and Serotonin Symptoms of SAD Treatments Conclusion