What Melatonin is

Melatonin is a hormone produced by the pineal gland from serotonin, released on a circadian rhythm and suppressed by light. Its role is chronobiotic rather than sedative: it signals biological night rather than inducing sleep directly, which is why its effect depends heavily on when it is taken relative to the body's own rhythm. That distinction is the single most misunderstood thing about it, and it explains why melatonin behaves nothing like a hypnotic. It is one of the few compounds in this catalogue that is genuinely endogenous rather than synthetic or analogue.

How Melatonin compares

Against prescription hypnotics: entirely different. Melatonin shifts circadian timing rather than sedating, and does not act at the GABA-A receptor. Against DSIP: melatonin has a well-characterised endogenous role and DSIP does not. Against ramelteon and other melatonin receptor agonists: those are synthetic compounds designed for the same receptors with different pharmacokinetics.