You already know volunteering is good for your community, but did you know it's also overwhelmingly good for your health? While a new report found that volunteering may help boost the mental health of those over 40, it's merely the latest in a string of studies that have consistently found volunteering is as good at keeping you mentally sharp and physically healthy as a daily dose of vitamins or exercise.

A recent study, which was published in the journal BMJ Open, surveyed 5,000 British families about their experiences with volunteering and their overall mental health. Participants completed the same survey every two years from 1996-2008.

About 20 percent of the survey participants reported doing regular unpaid work. Researchers found that these volunteers also scored highest on their mental health scores. The two were linked so directly that the more a person volunteered, the happier they were.

One could argue a chicken-and-egg theory: happier people are more likely to have the time, money, energy and resources to give back to others. But even when researchers adjusted for marital status, education, social class and overall health, the link was there, suggesting that the mental boost came from volunteering and not the other way around.

Any way you look at it, volunteering is good for you

This study follows up on a long line of research going back to 1988, showing how volunteerism can reduce the likelihood that a person will develop high blood pressure, dementia, and addiction while also experiencing less overall lifelong pain. One Canadian study found that teenagers who volunteered in an after-school program lost weight and had lower cholesterol levels than their non-volunteering peers.

Those are some pretty good perks for just a few hours of work, right?

According to Dr. Stephen G. Post, professor of preventive medicine at Stony Brook University in New York and author of "The Hidden Gifts of Helping," when you help others, your brain releases feel-good chemicals such as oxytocin, dopamine and serotonin, and these hormones can do more than just give you a warm, fuzzy glow. "They can also help cells repair themselves, store nutrients and grow," says Dr. Stephanie Brown, an associate professor of preventive medicine at Stony Brook University. And this translates to overall better health.

"Getting away from yourself, reaching out and contributing to the lives of others, especially in hard times when people are anxious about economic conditions, is a very healthy thing," said Post.

Give like you mean it

So volunteering can help improve both your physical and mental health — on one condition. You have to mean it. "If you are helping out of a sense of obligation, it may not be beneficial to your health," said Brown. In fact, it may just add to your stress.

An observational 2012 study found that people who volunteered for "self-oriented" reasons, either because they were forced to do so for work or school or because they were trying to get away from problems in their lives, had a mortality risk that was similar to those who didn't volunteer at all. It was only when people were volunteering out of a true sense of compassion that they saw any health benefits.

So whether it's restacking books at the library or walking dogs at the animal shelter, find a cause that's important to you and give it a try. Volunteering is a great way to foster a sense of connection that not only helps your community, but may also be good for you.

Volunteer to help others (and help yourself)
Research consistently shows that volunteering is good for your health — but only on one condition.