is a major health problem in the Untied States and one of the most common psychiatric illnesses. It is estimated that up to 40% of patients seeing primary care physicians
exhibit some depressive symptoms. It has been observed that in a subpopulation of depressed patients, their depressive episodes vary seasonally. The term applied to this pattern is Seasonal Affective Disorder or SAD. SAD is defined as a pattern of recurring depressive episodes with seasonal onset and remission. The majority of patients experience worsening of their symptoms in the winter. SAD is more prevalent at higher latitudes where there is more seasonal variation in climate and less light during winter months. The true prevalence of SAD is hard to determine due to overlap with other disorders, however estimates place the prevalence at about 1%-9% of population in western cultures. The pathogenesis of SAD may involve the effect of environmental light levels on the level of the neurotransmitter serotonin produced in the brain.
Although the biological mechanism of the disease is unclear, clinical studies have validated the SAD is indeed a real and treatable disorder. In fact, SAD is not really considered a separated diagnosis from depression in the DSM IV (the manual of diagnostic criteria for psychiatric disorders). Rather, SAD is considered a subset or modifier of the diagnosis of major depressive disorder. Any individual with SAD or any other symptoms of depression should visit a psychiatrist
as soon as possible for a full evaluation. Depression and SAD are serious but treatable disorders and it is advisable to be evaluate in person by a psychiatrist as soon as possible to void the substantial morbidity and even mortality associated with these disorders.