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Depression caused by light deprivation has been explained as having a biological origin. This article will examine the possible psychological relationship between depression and an individual's reaction to light.
Several explanations have been proffered regarding the source of depression in general. It has been explained as psychologically based, biologically based, or some combination of the two. Biologically based depression is usually attributed to genetic and/or chemical factors. Investigators of light-induced depression are in the biological camp and suspect a hormonal cause for this condition. Current research is examining other variables.
Rosenthal, Sack, and Gillin (1984) first proposed a syndrome called seasonal affective disorder (SAD) as a subcategory of depression. They also noted that this disorder would be responsive to light therapy. A good summary of the research on light-induced depression is provided by Wehr and Rosenthal (1989), who indicate that, historically, the relationship between light and depression, especially as it relates to seasonal changes, had been noticed by such authorities as Aristotle and Hippocrates. The shorter days of winter lead to less available daily light, and thus the condition would appear.
Light therapy is far from new. Treating depression with a powerful light source was recorded as early as the second century. Wehr and Rosenthal cite the Cappadocian, Aretaeus, who recommended that “lethargics are to be laid in the light and exposed to the rays of the sun (for the disease is gloom)” (p. 832).
Wehr and Rosenthal (1989) state that Pinel and his student Esquirol were the first to delineate winter and summer subtypes