A five-year study of 3,500 people living in three different US cities found that optimistic people fall asleep faster, sleep better and longer, and are generally better rested than their less-optimistic peers.

While the causal relationship between optimism and sleep isn’t determined by the study, one theory is that the behaviors that ultimately make people more optimistic also can lead to more restful sleep (as opposed to the idea that optimism itself leads to better sleep).

“Optimists are more likely to engage in active problem-focused coping and to interpret stressful events in more positive ways, reducing worry and ruminative thoughts when they’re falling asleep and throughout their sleep cycle,” said the study’s author, Rosalba Hernandez, a professor of social work at the University of Illinois.

Get the full story at inc.com.