In its simplest form, the serotonin deficiency theory of depression postulates that there is a net reduction in serotonin transmission in depressive illness. The pathophysiological change may result from two different mechanisms. The first involves a decrease in serotonin (5-HT) availability which has the consequential effect of compensatory receptor up-regulation or super sensitivity. The second mechanism implies a primary defect in receptor activity and/or signal transduction. The objective of this review is to analyze the serotonin system in depression as it relates to the above two postulates.
Kerr, Christopher W.
"The Serotonin Theory of Depression,"
Jefferson Journal of Psychiatry:
1, Article 4.
Available at: http://jdc.jefferson.edu/jeffjpsychiatry/vol12/iss1/4