Hydroxytryptophan is serotonin. If like me you have been clinically depressed on and off for seven years and on SSRIs from the docs (Selective serotonin reuptake inhibitors) i.e. citalopram; escitalopram, etc - then do what I did sooner than I did and get off them. It took me a whole year of cutting down bit by bit - that's how addictive they are. I tried cold turkey and ended up worse off than when i started. Then get these. No side effects. No downside (except the cost). They work. You sleep better, feel better and can think better. Google serotonin to find out what happens when your brain doesn't produce enough. Not fun. In fact debilitating to the extreme. How do I know they work and it's not just a placebo? because i stopped taking them, thinking they were just another health shop rip-off (50% more expensive than here for exactly same product). My wife bought me some more - at least I thought she did, she just got vitamins and put them in the old bottle. After a week i felt awful. Could not understand it. After a month I was as bad as I used to be. So back on the genuine item, unknown to me three weeks later. After a week I felt better. I did not know what my amateur scientist wife had done but was very grateful she had as she effectively cancelled any placebo effect. For me they work. Can't guarantee they will for you of course as your illness may be due to causes other than lack of serotonin. But the simple fact is, they are safe and have none of the horrific sideeffects of the drugs. What were they? Three stone on in weight in two years. It took me six months to get that off after i stopped the drugs. Depression. What's the point of antidepressants that depress you? Dizzy. Lack of concentration. Didn't care if i lived or died. Listlessness. Horrific nightmares. Need I go on? I would be interested to hear what other users of this think.