5-HTP is serotonin, one step upstream. Your brain builds serotonin from tryptophan, but the first enzyme in that chain is a bottleneck. 5-HTP is the intermediate that sits just past it, so a small oral dose raises serotonin where whole tryptophan barely moves the needle ¹. After dark the brain turns some of that serotonin into melatonin, which is why an evening dose reads as a sleep aid.

The sleep effect is the solid one. Fifty years of small trials land in the same place: a bedtime dose trims sleep-onset latency by roughly ten to twenty minutes, biggest for poor sleepers, near-invisible for good ones, and the night that follows looks normal rather than sedated ^{2 3}. The appetite effect is real but smaller: obese women on 900 mg a day ate less and lost about three kilograms more than placebo over twelve weeks ⁴. Depression is where the claim collapses — the Cochrane review found only two adequate trials, sixty-four people between them ⁵.

Check your medication list before anything else. If you take any serotonergic prescription, stop here. Otherwise, start low and take it at night.

The three effects arrive on different clocks. Sleep onset lands the first night: the gap between lights-out and asleep is just shorter ². Appetite loosens over the first week — the afternoon snack reach feels less automatic ⁴. Mood, if it shows at all, takes a month, closer to an antidepressant's timeline than a sleeping pill's. Past that, most people find the effect fades on a continuous run and prefer a few weeks on, a week off.