Not getting enough sleep? That could be making you more selfish

(CNN) — Sleep is widely recognized as one of the essential processes of life, providing powerful benefits on physical health, mental health, and even mortality.

But did you know that sleepless nights can also lead to selfish behavior?

Lack of sleep affects how likely a person is to help someone else, according to new research published in the journal PLOS Biology on Tuesday.

Researchers at the University of California, Berkeley, conducted three studies in the United States on this “selfish” effect, looking at changes in neural activity and behavior that benefit others, and found that it was prevalent even after a small loss of sleep.

Research scientist Eti Ben Simon and Matthew Walker, a professor of neuroscience and psychology at UC Berkeley and director of the university’s Human Sleep Science Center, led the study. They told CNN that this finding was very surprising.

“Even one hour of sleep loss was more than enough to influence someone else’s decision to help,” said Ben Simon, a postdoctoral fellow in psychology at the Center for the Science of Human Sleep. “When people lose an hour of sleep, there is a clear impact on our innate human kindness and our motivation to help others in need.”

Looking at a database of 3 million charitable donations between 2001 and 2016, Ben Simon, Walker and their colleagues observed a 10% drop in donations after the DST change. This drop was not observed in the states that do not follow the transition from one hour forward.

In the second study, researchers used fMRI to look at brain activity in 24 people after eight hours of sleep and after one sleepless night. The prosocial neural network, the brain areas associated with theory of mind, was less active after sleep deprivation, this study found.

Theory of mind is the ability to consider the needs, states, and emotions of other people, which typically develops in early childhood with socialization.

In the third study, which measured the sleep of more than 100 people for three or four nights, researchers unexpectedly found that sleep quality was more important than sleep quantity when it came to measuring selfishness. The team assessed levels of selfishness based on responses to questionnaires that study participants had completed. Both the amount and quality of sleep often influence emotional and social behavior, so the team expected to find an effect on both, Ben Simon told CNN.

“These findings might suggest that once sleep duration exceeds a nominal baseline amount, then it appears to be the quality of that sleep that is most critical in helping and supporting our desire to help other people,” he explained.

More than half of all people in developed countries say they don’t get enough sleep during the work week, which Walker calls a “global epidemic of sleep loss.” Extensive research has already shown links to mental health disorders like anxiety and depression, as well as physical ailments like diabetes and obesity.

Now, as the availability of evidence about its negative impact on social behavior increases, it could have consequences for society today, Walker added.

Ben Simon and Walker hope that their research will enable people to catch up on a full night’s sleep without the shame or stigma of laziness.

“(Sleep loss) radically alters how we are as social and emotional beings, which one could argue is the very essence of human interaction and what it means to live a full and meaningful human existence,” Walker said.