Seasonal affective disorder (SAD), also known as winter blues or winter depression, was first identified by Rosenthal et al. in 1984. Typically, symptoms of SAD are seen in the winter months due to decreased exposure to sunlight. The disorder is seen in individuals diagnosed with major depressive or bipolar I and II disease, as described in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR), and occurs mostly in the winter, in individuals who have normal mental health for most of the year. The symptoms are repetitive and include depression, sleep deprivation, decreased energy, and cravings for sweets and starchy foods. Although symptoms can be severe, they usually resolve in the spring and summer with the return of longer daylight hours. Although the physiologic basis of SAD is not clear, there are several theories of pathophysiology related to SAD; however, none have been strongly supported by research.
According to the American Psychiatric Association (APA), SAD has been linked to biochemical imbalances in the brain and is caused by shortening of daylight hours and lack of sunlight in the winter. It is suggested that the farther away from the equator an individual lives, the more likely it is that they will develop SAD.
A home-use light box is a treatment for individuals diagnosed with SAD. The prescribing healthcare provider will specify the treatment instructions regarding distance from the light box, amount of exposure time, and amount of lux (a unit of illumination) to be used.
