According to Iovieno et al. (Iovieno, N., Dalton E. D., Fava, M. & Mischoulon, D.,
“Second-tier Natural Antidepressants: Review and Critique,” Journal of Affective
Disorders 130(3):343-57 (2011)), 5 - HTP has been used clinically for over 30 years for
the treatment of depression. Most studies of the use of 5-HTP for depression were
conducted 20 or more years ago, at a time when there was a great interest in the
serotonin hypothesis of depression. Its use declined dramatically when tryptophan was
banned, but it is making a strong comeback.
Iovieno et al. describe all of the old studies and conclude that “results from the
published trials suggest that 5-HTP may have some efficacy in the treatment of
depression and may deserve to be evaluated in more rigorous studies in order to
conclusively establish its effectiveness, both as monotherapy and as augmentation.”^3
However, they warn, the older research is defective. A 2002 systematic review of
published clinical trials in which 5-HTP and L-tryptophan were used in depression found
that only two of the 108 examined trials were of sufficient quality to meet the inclusion
criteria for a meta-analysis.
Mischoulon concludes that tryptophan/5-HTP is one of the safer of the natural
products available for mood disorders, and previous evidence is supportive of its use
for depression and anxiety, but “larger and more rigorous studies are needed to clarify
its place in the psychiatric armamentarium.” Mischoulon says that though it appears
to act like an SSRI, he still would like to see a new wave of more rigorous research
with current preparations before he proceeds to recommend it on the same platform
with the better-tested SSRIs.
Before it was banned by the FDA (from 1991-2002), tryptophan was successfully used
to supplement standard tricyclic antidepressants. Two meta-analyses, in 2004^4 and
2006,^5 showed modest support for the use of 5-HTP as an adjunct to tricyclic anti-
depressants in the treatment of depression. As with tryptophan, the clinical activity of
5 - HTP is believed to be primarily due to its ability to act as a precursor of serotonin
synthesis and increase central nervous system levels of serotonin.
sharon
(sharon)
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