Night sickness is a sickness described by "flashes" of memories from deep inside the minds of workers beneath the icy surface of P3R-118. It is highly likely this term is a cover excuse for one who has had their lives of previous memories wiped. If one has night sickness, they are immediately confined, their memories re-stamped. When the members of SG-1 had their memories stamped with new ones, they were all said to be experiencing night sickness. (SG1: "Beneath the Surface")