Abi knows the drill by now. At least once every couple of months, her mother and I pack up a bunch of clothes and electronics and other stuff we’ve outgrown, load the boxes into the car and drive down to the local Goodwill donation center. At 5 years old, Abi still giggles at the ding-ding of the driveway bell as we pull into the unloading area. But recently our arrival at the loading zone triggered a different response from the back seat.

“Hey!” Abi said. “Did you guys sneak into my room and steal my toys?”

My wife and I exchanged a glance of incredulity and stifled a laugh. We turned to gently correct our daughter. Overlooking the criminal accusation, we told her we were only giving away things we no longer used (no toys were packed up… this time). Then we reminded her why we were there. We’re lucky, we told her. We have lots of things other families don’t have. This is our way of giving back.

As any parent knows, this is just part of a larger mission, along with nudging our child to give grandma a hug after receiving a lollipop or cuing up the “What do we say?” refrain when the checkout clerk issues an offhand compliment about her Wonder Woman T-shirt. We try to raise grateful kids because we don’t want brats who grow into entitled adolescents and self-centered young adults.

We do it, perhaps subconsciously, because we know we grown-ups also need an occasional reminder to assess and be thankful for what we have. We want to be better people and be surrounded by better people.

Now there is another reason to live by and spread the Gospel of Gratitude—it’s good for your health. Across the country, researchers and scientists in the field of positive psychology have been amassing evidence that thankfulness has a wide range of mental and physical health benefits. “Left to their own devices, our minds tend to hijack every opportunity for happiness,” says Robert Emmons, professor of psychology at the University of California, Davis. “Negativity, entitlement, resentfulness, forgetfulness and ungratefulness all clamor for our attention. Weighed down by negativity, we are worn down, emotionally and physically exhausted. Gratitude is our best weapon, an ally to counter these internal and external threats that rob us of sustainable joy.”

Emmons is founder and director of the Emmons Lab at UC Davis, where he and his team are at the forefront of a growing body of research that provides hard data to back up the philosophy that gratitude can improve our health. Through various practices, such as having people keep daily journals of gifts and graces, Emmons and his colleagues have observed a wide range of psychological and physical benefits, ranging from lowering blood pressure and cholesterol to reducing anxiety and the risk of depression. Other researchers point out that expressing gratefulness also improves interpersonal connections—all from just taking a minute or two to stop and say “thank you” to a co-worker who helped you in a bind or a friend who baked you cupcakes.

“In gratitude, we focus on the giftedness of life,” Emmons says. “We affirm that goodness exists, even among the rancor of daily life. This realization is freeing, redeeming. Gratitude works.”

***

Sure—but how does it work? How does a diary of blessings or a “thx!” text function as such a cure-all? Although the physiological science behind the connection is still a bit murky, Emmons says that from a behavioral and psychological standpoint, gratitude heals simply by overcoming and blocking out the general negativity that causes the stress from which so many maladies stem.

“Gratitude is our best weapon, an ally to counter these internal and external threats that rob us of sustainable joy.”

Having an overall focus on the positive triggers the parasympathetic part of the nervous system that eases stress. In fact, research at UC Davis has linked gratitude with a 23 percent decrease in levels of cortisol, the stress hormone. That relief alone can have far-reaching health benefits. For instance, in one Emmons study, subjects who kept a gratitude diary for two weeks showed a sustained 28 percent reduction in perceived stress and a 16 percent drop in perceived depression.

The UC Davis study also showed that two activities—counting blessings and penning thank-you letters—reduced the risk of depression in at-risk patients by 41 percent over six months. Subjects keeping journals took in less dietary fat by as much as 25 percent, and grateful respondents’ Hemoglobin A1c, a marker for diabetes, dipped by between 9 and 13 percent.

Emmons and his colleagues at UC Davis are not alone in their quest to discover why expressing gratitude makes us healthier. A paper published by faculty at the University of Kentucky and the University of Louisville observed that overworked law students who had optimistic outlooks—which have been linked to gratitude—showed heightened immune systems.

In 2015 Paul Mills, professor of behavioral medicine and public health at the University of California, San Diego School of Medicine, spearheaded a study of 186 men and women around the age of 66, who had all suffered some sort of heart damage. Each filled out a questionnaire asking about the people, places and things they most appreciated. Mills and his team found that those people who were most grateful were less depressed, slept better, were more energetic, and, after a blood test, showed the lowest levels of heart inflammation and plaque buildup in their arteries. A follow-up revealed that patients who kept a gratitude journal for two months showed reduced inflammation and improved heart rhythm. “There’s an old axiom that ‘A grateful heart is a healthy heart,’ ” Mills says. “Those who showed more gratitude were certainly better off than those who didn’t.”

UC Davis studies have shown that grateful hearts have 16 percent lower diastolic blood pressure and 10 percent better systolic numbers. Mills, who specializes in disease process, says he doesn’t really know exactly how being thankful kick-starts our hearts.

But he has a theory. “When I bring into my mind an attitude of gratitude, I immediately feel more connected, not only to myself, but to my environment—the opposite of how I feel when I’m stressed or depressed, when we retreat into ourselves,” he says. “Gratitude helps us reconnect with the world around us. When we are connected, we’re less stressed. We are social beings. And when we have less stress, we experience all the downstream benefits.”

***

The bulk of these studies deal with the internal perks of a grateful attitude. But in order to get the maximum benefit, we have to do more than think about gratitude and jot it down in our private journals. After all, what good is a thank-you note if it’s never sent?

Emmons says personal awareness of what we’re thankful for is only the first step. Expressing that gratitude, either verbally or through an action or gesture, is how we build successful and supportive relationships. “Without gratitude we’d be in relational ruin,” Emmons says. “Organizations and societies would crumble.”

“Gratitude requires empathy, it tunes you into the goals of another so that you can be more supportive of their efforts and sensitive to their needs,” says Giacomo Bono, assistant professor of cognitive and applied psychology at California State University, Dominguez Hills.

He says that helping others puts you in a better position to help yourself. “We don’t achieve things without taking chances,” Bono says. “We have to put ourselves out there, and a lot of times, we might not do that on our own. But if you have one or two good colleagues who are supportive of your efforts, then you’re more likely to take a chance. And without taking that chance, you’ll never know your capacity.” Bono points out that this give-and-take is the foundation for all of our social and business networks because expressing gratitude is key in developing trust.

Bono has done a lot of work in observing and teaching gratitude to children. But he says the beauty of this psychological and physical salve is that even if your parents or teachers didn’t drill it into you as a kid, you can pick it up any time.

For anyone looking to tap into the healing power of thankfulness, he recommends keeping a journal or a list of people, places and things you’re grateful for. This will serve as a daily reminder to be on the lookout for the positive. Also try to express your gratitude more regularly by saying “thank you,” or even giving a fist bump or a high five, if it’s appropriate.

“In gratitude, we focus on the giftedness of life,” Emmons says. “We affirm that goodness exists, even among the rancor of daily life.”

Rather than just dashing off a terse email, Bono advocates reviving the lost art of sitting down with a pen and handwriting a letter or note that you can deliver personally. The extra effort will emphasize how much you appreciate the recipient’s help. “A thoughtful note of thanks slows life down and focuses on the benefactor and on the fact that their efforts mattered to you,” Bono says. “With the fast pace of life, just slowing down is important. Mindfulness is healthy. Slow down and appreciate it.”

Whether you’re penning a note on personalized stationery, scribbling in a journal or just meditating, a deep contemplation of gratitude will probably be a tune-up for your mind and body in many ways—including some we might not yet even know.

Back at the Emmons Lab at UC Davis, the institution’s namesake says the research into the science of gratefulness continues. Next on the agenda: gratitude’s connection with joy. “I am most intrigued with how gratitude rescues us from negativity,” Emmons says. “Joy, we feel, is much more basic to flourishing and well-being than happiness, which is more of a cognitive judgment, whereas joy is a basic emotion. We hypothesize that gratitude is the foundation for joy, since gratitude is the relationship-strengthening emotion, and joy is fundamentally and foundationally about connection.”

Meanwhile, back home, Abi is probably too young for journaling or letter writing, beyond a quick note. But maybe we’ll start sitting down on a regular basis and making a list of our blessings. Along with prompting empty, muttered “thank yous,” we’ll take a second or two afterward to dig beneath the autopilot politeness and mine the true reason she should be appreciative.

And the next time we make a Goodwill run, maybe it’ll be time for us to give Abi an empty box and ask her to choose the toys and books she feels she can part with—items she thinks some other girl or boy might enjoy. To focus on what she has, what we all have as a family, and why some of these things might be more valuable to others.

We know it will be a hard lesson. But hopefully, one day, she’ll thank us.