TRYPTOPHAN/5-HYDROXY-L-TRYPTOPHAN (5-HTP) FOR ANXIETY, FOR
DEPRESSION AND TO ENHANCE THE EFFECTIVENESS OF
CONVENTIONAL ANTI-DEPRESSANTS
SUMMARY
WHAT WE KNOW
Tryptophan, an amino acid, is a precursor of serotonin and has been used since the 1970s to
increase brain levels of serotonin. 5 - HTP (5-hydroxy-L-tryptophan) is a modern variant, now
extensively marketed in the United States. Before it was temporarily banned by the FDA (from
1989 - 2002), tryptophan was successfully used to supplement standard tricyclic antidepressants.
It has been used successfully with MAOIs. Two meta-analyses, in 2004 and 2006, showed
modest support for the use of 5-HTP as an adjunctive treatment for depression. Earlier studies
had shown modest effectiveness for anxiety. As with tryptophan, the clinical activity of 5-HTP is
believed to result primarily from its ability to act as a precursor of serotonin synthesis and
increase central nervous system levels of serotonin.
MENTAL HEALTH IMPLICATIONS
Depression and Anxiety
There are insufficient data to recommend use of tryptophan or 5-HTP, but there is enough
promise to merit further research and cautious experimentation if standard treatments for
depression or anxiety are ineffective or poorly tolerated. Mischoulon concludes that it 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. 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