Seasonal affective disorder (SAD), also known as winter depression, winter blues, summer depression, summer blues, or seasonal depression, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or summer, spring or autumn year after year. In the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), SAD is not a unique mood disorder, but is "a specifier of major depression".
Although experts were initially skeptical, this condition is now recognized as a common disorder, with its prevalence in the U.S. ranging from 1.4 percent in Florida to 9.7 percent in New Hampshire.
The U.S. National Library of Medicine notes that "some people experience a serious mood change when the seasons change. They may sleep too much, have little energy, and may also feel depressed. Though symptoms can be severe, they usually clear up." The condition in the summer is often referred to as reverse seasonal affective disorder, and can also include heightened anxiety.
SAD was formally described and named in 1984 by Norman E. Rosenthal and colleagues at the National Institute of Mental Health.
There are many different treatments for classic hormones (winter-based) seasonal affective disorder, including light therapy with sunlight or bright lights, antidepressant medication, cognitive-behavioral therapy, ionized-air administration, and carefully timed supplementation of the hormone melatonin.