Honesty could boost your health.

That according to a study that found that telling fewer lies benefits people physically and mentally.

Anita Kelly, a psychology professor at the University of Notre Dame, had 110 people between 18 and 71 years old take a lie-detector test every week for 10 weeks and complete health and relationship assessments.that looked at the number of times they’d lied each week.

“When they went up in their lies, their health went down,” says Kelly. “When their lies went down, their health improved.”

Linda Stroh, a professor emeritus of organizational behavior at Loyola University Chicago, says the findings are consistent with her research on trust. “When you find that you don’t lie, you have less stress,” Stroh says. “Being very conflicted adds an inordinate amount of stress to your life.”

Past research suggests that Americans average 11 lies a week. Kelly says the no-lie group was down to, on average, one lie a week. For both groups, when participants lied less in a given week, they reported their physical and mental health to be significantly better that week.