The researchers compared animals who were deprived of sleep for 72 hours with others who were not. They found those who missed out on rest had higher levels of the stress hormone corticosterone. It would be interesting to see if partial sleep deprivation - getting a little bit less sleep every night that you need - had the same effect

They also produced significantly fewer new brain cells in a particular region of the hippocampus. When the animals’ corticosterone levels were kept at a constant level, the reduction in cell proliferation was abolished. The results suggest that elevated stress hormone levels resulting from sleep deprivation could explain the reduction in cell production in the adult brain.

Sleep patterns were restored to normal within a week. However levels of nerve cell production (neurogenesis) were not restored for two weeks, and the brain appears to boost its efforts in order to counteract the shortage.