 While the former typically experience more confined conditions, the airline cabin crew tend to experience more symptoms associated with sopite syndrome; this effect may be attributed to the lack of visual validation and increased movement of the cabin crew.Certain hormones or biochemicals likely affect the pathways associated with motion sickness in general and the sopite syndrome in particular.Studies reported by Kennedy, Drexler and Kennedy (2010) have investigated the role of cortisol and melatonin (a hormone associated with the maintenance of circadian rhythms) in motion-induced drowsiness.