5-htp is a serotonin precursor (similar to l-tryptophan) that crosses the blood-brain barrier, it's been shown in clinical trials to have an antidepressant effect. (at a high enough dose it was on par with SSRIs, and it worked well in conjunction with SSRIs) Has anyone used this supplement? I used it for a little bit, and it seemed to help some, but I can't say for certain because I'm not using it now and my medications are very different than they were then.
“Is God willing to prevent evil, but not able? Then he is impotent. Is he able, but not willing? Then he is malevolent. Is he both able and willing? Whence then is evil?” - Epicurus