Melatonin stands apart from every other entry in this Atlas: it isn't a traditional plant or food remedy passed down through folk medicine, but a hormone your own body produces, only scientifically identified in 1958 by Yale dermatologist Aaron Lerner, who was actually researching skin pigmentation in frogs rather than sleep. Lerner named it "melatonin" after observing it caused frog skin cells to lighten, and it took further decades of research to establish its central role in regulating the human sleep-wake cycle.
Its inclusion here reflects a different kind of story than the ancient traditions covered elsewhere in the Atlas: melatonin represents modern biochemistry identifying and then commercializing a substance the body already makes naturally, rather than a substance discovered through generations of trial-and-error folk use. It became available as an over-the-counter supplement in the United States in the 1990s and has since become one of the most widely used sleep aids worldwide — genuinely useful context for understanding both its appeal and its real, if more modest than commonly assumed, effects.
Melatonin has real, replicated evidence for reducing the time it takes to fall asleep (sleep onset latency), though the effect size is more modest than its popularity might suggest. A comprehensive dose-response meta-analysis of 26 randomized controlled trials (1,689 observations) found melatonin reduces sleep onset latency and increases total sleep time, with effects peaking around a 4mg dose taken roughly three hours before desired bedtime — notably different from how many people actually take it (a smaller dose closer to bedtime). A separate network meta-analysis supported melatonin's effectiveness specifically for sleep-onset difficulties, when compared against other insomnia interventions.
The nuance worth knowing: a more recent 2022 meta-analysis focused on chronic insomnia found that melatonin was only significantly effective for sleep onset latency and total sleep time in children and adolescents when insomnia had no other underlying condition — the picture for general adult chronic insomnia was less consistent across studies due to substantial heterogeneity. Cognitive behavioral therapy for insomnia (CBT-I) consistently outperforms melatonin and every other intervention studied in these comparisons, a finding worth knowing given how much more heavily melatonin is marketed than CBT-I.
Not applicable — melatonin is not a traditional herbal or food preparation; it is manufactured as a synthetic supplement designed to mimic the naturally-occurring hormone.