MELATONIN AND ADJUSTMENT TO PHASE-SHIFT

The pineal hormone melatonin has clear circadian phase-shifting effect s in humans which have recently been formalized as a phase response cu rve. Its potential use in circadian rhythm disorders has been investig ated in field studies of jet lag and shift work and in simulated phase shift. A substantial amount of information indicates that in the majo rity of subjects it hastens adaptation of both subjective and objectiv e measures to forced shifts in time cues with few reported side-effect s. Field studies of its use in adaptation to shift work are sparse and preliminary but the first indications are positive. In some blind sub jects with sleep disturbance it can stabilize sleep onset time without necessarily entraining all circadian rhythms and it can advance sleep timing in delayed sleep-phase insomnia. Acute suppression of core bod y temperature may be an integral part of the phase-shifting mechanism.