All other things being equal, parents scored 4.5 points lower than non-parents in systolic blood pressure (the top number) and 3 points lower than non-parents in diastolic blood pressure. Holt-Lunstad says the size of the difference is statistically significant, but she warns against hastily making major life changes based on this finding alone.

"This doesn't mean the more kids you have, the better your blood pressure," Holt-Lunstad said. "The findings are simply tied to parenthood, no matter the number of children or employment status."

The effect was more pronounced among women, with motherhood corresponding to a 12-point difference in systolic blood pressure and a 7-point difference in diastolic blood pressure.

And if fulfilling relationships make your body feel better, it's no surprise what stressful relationships can do. See this story on "frenemies" for more about that.

Source: Brigham Young University