Other studies have confirmed these reports of paranoid delusions, some of persecution, as well as defensiveness. Thought disturbances during sleep deprivation, in conjunction with spontaneous laughter and postural abnormalities, have been observed to occur in waves, interspersed by periods of apparently normal behaviors. Though remarkable physical ailments caused by extended wakefulness have not been reported, there are reports of deficits in some areas. One of the most common findings is itching and burning of the eyes. Closing of the eyelids is the only thing that alleviates this, which makes it extremely difficult to stay awake.
Eye irritation is exacerbated during the night.
One experiment reported that over a third of participants experienced headaches during sleep deprivation, some of these headaches being continuous. That same experiment reported increases sensitivity to pain. This hyperalgesia was confirmed in other studies, in which it was also shown that there is no change in the sensitivity to touch. The recovery of total sleep deprivation is an interesting phenomenon. It involves two distinct phases of rebound.