Aqui estão os resultados do meta-estudo sobre o jet lag (ênfase minha):
Eight [37–44] RCTs with 972 total participants characterized melatonin use for counteracting jet lag. Almost all of the studies were of high (+) quality [37, 39–44], with the exception of one poor (−) quality study [38], which favored neither melatonin nor control, despite a large sample size (n = 339). Of the seven high (+) quality studies, one [40] favored neither melatonin nor control. The remaining six [37, 39, 41–44] RCTs favored melatonin, including two [42, 43] large studies (n = 320 [44] and n = 160 [41]) and one [39] which noted a limitation that melatonin increased tiredness the next morning. Melatonin appears to be relatively safe based on the six [38, 39, 41–44] studies that reported adverse events, citing occasional, but not serious adverse events and interactions. Based on the high quality and favorable results reported, the [subject matter experts] concluded that in a jet lagged population, further research may have an impact on the confidence in the estimate of the effect, and as such, provide a weak recommendation in favor of melatonin use for rebalancing the sleep-wake cycle in people with jet lag.
Fonte:
Costello, R.B., Lentino, C. V., Boyd, C.C., O'Connell, M.L., Crawford, C. C., Sprengel, M. L., & Deuster, P. A. (2014). A eficácia da melatonina na promoção do sono saudável: uma rápida avaliação de evidências da literatura. Nutrition Journal, 13, 106. link