Other symptoms include the usual features of depression, especially decreased sexual appetite, lethargy, hopelessness, suicidal thoughts, lack of interest in normal activities, and social withdrawal. Recurrent summer depression is more likely to be characterized by insomnia, decreased appetite, weight loss, and agitation or anxiety. Patients with SAD in the summer often have histories of summer trips to the north, where they find relief from depression in cold climates. Generally, normal air conditioning is not sufficient to relieve depression in these patients during the summer months. Symptoms of winter SAD usually begin in October or November and subside in March or April.
Depressions are usually mild to moderate, but they can be severe.
The most common characteristic of people with SAD is their reaction to changes in environmental light. Patients living at different latitudes note that their winter depressions are longer and more profound the farther north they live. SAD is often misdiagnosed as hypothyroidism, hypoglycemia, infectious mononucleosis, and other viral infections. Scientists believe that light therapy works by altering the levels of certain brain chemicals. Other antidepressants may also be of value.