5-HTP works by increasing the amount of serotonin manufactured in the brain. SSRI antidepressants have many side effects including impotence and they are expensive. Studies suggest that 5-HTP may work better than tryptophan, as it is 10 times better than tryptophan in elevating serotonin levels. SSRI's depend upon the presence of serotonin. 5-HTP creates serotonin.
Studies suggest that it works very well in patients unresponsive to standard anti-depressant drugs.
These patients had failed on all known anti-depressants and even that old horror, electroconvulsive therapy. 43 had a complete recovery and 8 more had a significant improvement. It seems to work particularly well in those who have aggression or panic disorders. The fenfluramine half of the now discredited and dangerous Fen-Phen combination worked by increasing serotonin levels. Beta endorphins also make people feel satiated.