Is Serotonin a Shared Chemical Pathway for Depression?
Serotonin, scientifically termed 5-hydroxytryptamine or
5-HT, was first discovered in research and crystallized 40 years ago. Neuroscientists have determined that 5-HT is a major neurotransmitter involved in a number of physiological processes such as sleep, thermoregulation, appetite control, sexual behavior, cardiovascular function, endocrine regulation and muscle contraction. Additionally, it is implicated in the "mechanism of action of various pharmacological agents (anxiolytic agents, antidepressants, hallucinogenic agents)" (Cannon, 1991, p. 132). After studying 5-HT for over 25 years Page concluded that "no physiological substance has been discovered that has such diverse actions in the body as serotonin" (Cannon, 1991, p. 132). The question which neuroscientists have been asking for over a decade is whether or not "all forms of depression ultimately operate through a shared chemical pathway" and whether that pathway could possibly be identified as serotonin? (Holden, 1991, p. 1450)
First, researchers agree that depression must be recognized as a "heterogeneous disorder" (Holden, 1991, p. 1450). It can be triggered by stress, biochemical dysfunction, illness or unknown causes. Yet clinical labels of description such as endogenous or reactive depression carry almost no relevance for treatment. Pharmaceutical research has overcome the bewildering heterogeneity of depression to produce antidepressant medication which have proved to be 70% effective. The majority of these antidepressants act on one or both of the major neurotransmitter systems, the serotonergic (which uses serotonin as a transmitter) or the norepinephrine (which uses norepinephrine) systems (Holden, 1991, p. 1451). These drugs block the "re-uptake of these neurotransmitters by the cells that send them" eventually leading to the regulation of mood, arousal, appetite and sleep (Holden, 1991, ...