Melatonin increases reactive aggression in humans
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Melatonin, a hormone released preferentially by the pineal gland during the night, affects circadian rhythms and aging processes. As animal studies have shown that melatonin increases resident-intruder aggression, this study aimed to investigate the impact of melatonin treatment on human aggression.
In a double-blind, randomized, placebo-controlled between-participant design, 63 healthy male volunteers completed the Taylor Aggression Paradigm (TAP) after oral administration of melatonin or placebo.
We found that when given the opportunity to administer high or low punishments to an opponent, participants who ingested melatonin selected the high punishment more often than those who ingested placebo. The increased reactive aggression under melatonin administration remained after controlling for inhibitory ability, trait aggression, trait impulsiveness, circadian preference, perceptual sensibility to noise, and changes in subjective sleepiness and emotional states.
This study provides novel and direct evidence for the involvement of melatonin in human social processes.
KeywordsMelatonin Reactive aggression Taylor aggression paradigm Antisocial behavior Circadian rhythm
We thank Professor Drew Dawson and Dr. Xuan Zhou from the University of South Australia for their suggestions on melatonin administration and Dr. Philip Blue for the preparation of the manuscript.
J. L. and R. Z. designed the experiment and analyzed the data, under the supervision of X. Z., J. L., R. Z., and W. X., and H. L. performed the experiment. J. L., C. E., and X. Z. wrote the manuscript.
Compliance with ethical standards
The experiment was performed in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of the Department of Psychology, Peking University.
This study was supported by grants from the National Basic Research Program of China (973 Program: 2015CB856400) and National Natural Science Foundation of China (31630034) to Xiaolin Zhou and the National Natural Science Foundation of China (31600928) to Jinting Liu.
Conflict of interests
The authors declared that they had no conflicts of interest.
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