Although evidences of sleep-dependent learning have now been condensed across a wide variety of mnemonic domains including emotional memory and fear-conditioned memory,it remains unknown whether sleep deprivation helps prevent posttraumatic stress disorder. We examined the effects of total sleep deprivation on subsequent enhancement of aversive event memory,implicit fear recognition,and fear conditioning in healthy humans. Results suggested that sleep deprivation extinguishes the fear-magnifying effects of memory during sleep, and that insomnia as an acute stress response might provide prophylactic benefits in reducing the development of posttraumatic stress disorder.