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The neurotrophic hypothesis of depression [1] proposes that major depressive disorder (MDD) is caused, at least partly, by impaired neurotrophic support.Neurotrophic factors (also known as neurotrophins) are a family of closely related proteins which regulate the survival, development, and function of neurons in both the central and peripheral nervous systems.
Proponents of the monoamine hypothesis argue that this lag is that the neurotransmitter activity enhancement is the result of auto receptor desensitization, which can take weeks. [59] Intensive investigation has failed to find convincing evidence of a primary dysfunction of a specific monoamine system in people with MDD.
The pharmacology of antidepressants is not entirely clear.. The earliest and probably most widely accepted scientific theory of antidepressant action is the monoamine hypothesis (which can be traced back to the 1950s), which states that depression is due to an imbalance (most often a deficiency) of the monoamine neurotransmitters (namely serotonin, norepinephrine and dopamine). [1]
Monoamine precursors are precursors of monoamines and monoamine neurotransmitters in the body. [ 1 ] [ 2 ] The amino acids L -tryptophan and L -5-hydroxytryptophan (5-HTP; oxitriptan) are precursors of serotonin and melatonin , while the amino acids L -phenylalanine , L -tyrosine , and L -DOPA (levodopa) are precursors of dopamine , epinephrine ...
The monoamine hypothesis was originally proposed based on observations that reserpine, a drug which depletes the monoamine neurotransmitters, produced depressive effects in people, [201] and that certain hydrazine antituberculosis agents like iproniazid, which prevent the breakdown of monoamine neurotransmitters, produced apparent ...
The criteria below are based on the formal DSM-5 criteria for a major depressive episode. [21] A diagnosis of a major depressive episode requires the patient to have experienced five or more of the symptoms below, one of which must be either a depressive mood or a loss of interest or pleasure (although both are frequently present). [ 1 ]
Based on the monoamine hypothesis of depression, which asserts that decreased concentrations of monoamine neurotransmitters leads to depressive symptoms, the following relations were determined: "Norepinephrine may be related to alertness and energy as well as anxiety, attention, and interest in life; [lack of] serotonin to anxiety, obsessions ...
However, the hypothesis is incomplete, as several lines of evidence suggests that depression is more than just a monoamine imbalance. For example, antidepressants usually take several weeks to reduce a patient's depressive symptoms, which is inconsistent with the finding that monoamine levels are affected within hours of using antidepressants. [5]