World Kindness Day: Being kind could help you live longer, experts say

"(Being kind) helps the immune system, blood pressure; it helps people to live longer and better," Kelli Harding of Columbia University in New York, who penned the book, "The Rabbit Effect," told the BBC. "It's pretty amazing because there's an ample supply and you can't overdose on it."

Daniel Fessler, with the University of California LA's Bedari Kindness Institute, agreed, calling kindness "therapeutic," and saying acts of kindness can treat depression and anxiety, according to Yahoo News.

Researchers at the University of British Columbia tested this idea by asking part of a group of 140 people with social anxiety to perform acts of kindness for four weeks.

When the month was up, those participants who showed kindness “were significantly more likely to report relationship satisfaction, as well as being less likely to avoid social situations.”

In addition to relieving depression and anxiety, scientists at Purdue University found those who volunteer have lower levels of the protein CRP, which is a marker of inflammation.

Inflammation has been linked to everything from depression and dementia to heart disease and cancer.

World Kindness Day, an international observance on Nov. 13, was introduced in 1998 by the World Kindness Movement with the goal of encouraging people around the world to show kindness to one another.

On Twitter, #WorldKindnessDay quickly became a trending hashtag, with people and organizations offering ways to be kind.