Sleep loss doesn’t just make us feel tired. It can undermine our emotional functioning, reduce our positive mood and lead us to exhibit symptoms of anxiety. These are the findings of a study published by the American Psychological Association in the journal “Psychological Bulletin”.

The research team, led by Kara Palmer of Montana State University, analyzed data from 154 studies spanning five decades with a total of 5,715 participants. In all studies the researchers disturbed the participants’ sleep for one or more nights. In some experiments participants stayed awake for an extended period of time, in others they were allowed less sleep than typical, and in a third category they woke up periodically throughout the night.

As found, sleep loss led in all cases to fewer positive emotions (such as joy, happiness, and contentment), as well as increased anxiety symptoms, such as a fast heart rate and increased worry.

However, a limitation of the study was that the majority of participants were young adults, with an average age of 23 years. According to the researchers, future research should include a larger age sample to better understand how sleep deprivation affects people at different ages.