BOZEMAN – Sleeping less does more than just make us tired. It can undermine emotional functioning, decrease positive moods and put people at higher risk for anxiety symptoms, according to a study led by a Montana State University professor who synthesized more than 50 years of research on sleep deprivation and mood.

“In our largely sleep-deprived society, quantifying the effects of sleep loss on emotion is critical for promoting psychological health,” said Cara Palmer, assistant professor in the Department of Psychology in MSU’s College of Letters and Science and lead author of the paper published Dec. 21 in the journal Psychological Bulletin. “This study represents the most comprehensive synthesis of experimental sleep and emotion research to date and provides strong evidence that periods of extended wakefulness, shortened sleep duration and nighttime awakenings adversely influence human emotional functioning.”

Palmer and her colleagues analyzed data from 154 studies spanning five decades, with 5,715 total participants. In all those studies, researchers disrupted participants’ sleep for one or more nights. In some experiments, participants were kept awake for an extended period. In others, they were allowed a shorter-than-typical amount of sleep, and in others they were periodically awakened throughout the night. Each study also measured at least one emotion-related variable after the sleep manipulation, such as participants’ self-reported mood, their response to emotional stimuli and measures of depression and anxiety symptoms.

Overall, the researchers found that all three types of sleep loss resulted in fewer positive emotions like joy, happiness and contentment among participants, as well as increased anxiety symptoms such as a rapid heart rate and increased worrying.

“This occurred even after short periods of sleep loss, like staying up an hour or two later than usual or after losing just a few hours of sleep,” Palmer said. “We also found that sleep loss increased anxiety symptoms and blunted arousal in response to emotional stimuli.”

Findings for symptoms of depression were smaller and less consistent. The findings were also more mixed for negative emotions like sadness, worry and stress.

One limitation to the study is that the majority of participants were young adults – the average age was 23. Future research should include a more diverse age sample to better understand how sleep deprivation affects people at different ages, according to the researchers.

“Research has found that more than 30% of adults and up to 90% of teens don’t get enough sleep,” Palmer said. “We still don’t know how sleep loss may affect long-term emotional functioning, especially for children or teens, but they may be more vulnerable to the impact of unhealthy sleep since they are undergoing rapid brain development.”

She said the implications of this research for individual and public health are considerable.

“Industries and sectors prone to sleep less, such as first responders, pilots and truck drivers, should develop and adopt policies that prioritize sleep to mitigate against the risks to daytime function and well-being,” Palmer said.

Palmer is the director of MSU’s Sleep and Development Lab and co-director of the MSU Sleep Research Lab. Her research focuses on how sleep impacts the social and emotional development of children, teens and young adults in ways that increase risk or resilience for mental health difficulties.

“My lab is currently working on several studies that investigate the intersection of sleep and emotional experiences in children and teens to better understand how sleep impacts both short-term and long-term emotional health,” Palmer said.

Yves Idzerda, dean of the College of Letters and Science, said Palmer is a renowned scientist whose research goes beyond identifying sources of sleep struggles but also looks at the consequences of poor sleep. He noted that her potential was recognized by the World Sleep Society in 2019, when she received its Early Investigator Award, and that the impact of her work was recognized by the Journal of Adolescent Health in 2020, when a study she authored was numbered among the journal’s Distinguished Dozen most-cited articles.