Sleepless nights can increase your chances of forming false memories.

Researchers asked volunteers to learn lists of words, each list relating to a particular topic. The researchers then tested their subjects’ memories after a night’s sleep or a night spent awake. They showed them the list of words again, having added a few extra words, and asked them to recall whether the words had been in the original list. The sleep-deprived group gave more false responses than the group allowed to sleep.

It may not be sleep deprivation itself that causes the formation of false memories, but the act of retrieving them from storage. When the team kept one group of people awake for one night, let them catch up on their sleep the next night, and then tested them, the volunteers had the same number of false memories as those who hadn’t been sleep-deprived at all.