Evidence Level
Emerging
5-HTP has a strong biochemical rationale as a serotonin precursor, but clinical trial evidence is limited and older. Poldinger et al. (1991) provided the most significant evidence, comparing 5-HTP to fluvoxamine for depression and finding comparable efficacy. Shell et al. (2010) demonstrated sleep benefits with a GABA/5-HTP combination. Byerley et al. (1987) reviewed early clinical trials and found generally positive results for depression, though study quality was variable. The main concern is safety when combined with serotonergic medications — serotonin syndrome is a potentially life-threatening adverse reaction. For this reason, 5-HTP requires more careful clinical consideration than many other sleep/stress supplements.