CLEVELAND, Ohio — For those preparing to hit the sales this Black Friday, there’s something that might make holiday shoppers feel even better about forking over some hard-earned cash on their friends, relatives and coworkers; giving is good for your health.

It’s true. Doing something nice for someone else is a gift you give yourself.

And it’s not just the giving of holiday gifts. Any genuine act of generosity or altruistic service toward others returns a host of mental and physical health benefits to the giver. It doesn’t have to cost you anything, or even take a long time, research has shown.

Holding open doors. Carrying bags. Helping an elderly neighbor take their trash to the curb. Making a meal for a friend. Every act of kindness no matter how big or small, as long as it is freely given and an altruistic act, can have a bigger positive impact on your overall health and well-being than many medicines.

Over the years a slew of scientific research has supported the phenomenon that doing good is good for you. Givers have less depression and more elevated moods. They have lower blood pressure, better cardiovascular health, less stress and anxiety and lower rates of dementia.

There’s even evidence that people who frequently engage in helping others live longer than those who don’t.

The secret is in the fact that doing something nice for others releases chemicals in the brain that make us feel good. Things like serotonin that regulates mood, dopamine which is responsible for feelings of pleasure and satisfaction, and oxytocin which makes us feel connected to others.

“When we do things for other people, it makes us feel much more engaged and joyful,” writes Dr. Susan Albers a psychologist at the Cleveland Clinic. “That’s good for our health and our happiness.”

• Related: Looking for ways to show gratitude? Here’s how to get your family volunteering

Stephen Post, a former happiness researcher at Case Western Reserve University who is now the director of the Center for Medical Humanities at Stony Brook University in New York, has done a number of studies examining the impact volunteerism has on the lives of the volunteers.

In one, he and his colleagues looked at the long-term health of those who had volunteered in high school in the 1990s. What they found was that the benefits of volunteering lasted well into adulthood.

“The ones who take to this quite readily are relatively spared when it comes to self-destructive behaviors, addictions, and they tend to be healthier mentally and physically in midlife,” Post said.

But there is a caveat. To really be effective the activities can’t be forced, they must be something the giver chooses themselves and enjoys, and they must be something the user can share with others and be part of a community.

“A peer group is very important. We found that when people are doing this independently it’s not as effective,” said Post.

Interestingly, when it comes to the amount of time required to reap the benefits of volunteering, it turns out that age matters.

Teenagers benefit from as little as an hour of service a week, where as older adults need more like 3-4 hours a week.

Studies indicate that this can be accomplished, for example, by giving nursing home residents tasks that help engage them socially with the other residents – tending to plants or animals, or a room where groups of residents could put together baskets for others or knit scarves and socks for those in need.

The idea is that helping others can provide a sense of belonging, and a way to make new friends and connect with the community. Teenagers and young adults naturally have a much stronger social network than older adults for whom volunteering fills that gap.

All of this has actually led to a healthcare movement in the United Kingdom that Post helped start called “social prescribing,” in which doctors in medical setting “prescribe” social activities to their patients. The idea has its roots in the fact that around 20% of patients see their doctor for non-medical problems that nevertheless have a negative impact on health.

By deliberately addressing those non-medical needs for social connectedness and providing the personnel and resources to help their patients make those connections, they are improving the lives and health of their communities and saving healthcare resources.

“If you could put all this in some kind of a pill and sell it at CVS, it would be highly effective,” said Post. “On a scale of one to 10, if insulin is a nine for diabetes, and Aricept is about a 0.001 for Alzheimer’s, this would be about a seven or an eight, easy, because you’re actually helping people turn their lives around and their getting a lot of response from it.”

But why is it that being helpful, kind and connected to our communities in positive ways is good for us? Isn’t looking out for oneself an evolutionary advantage?

Psychologists like Abigail Marsh believe the answer is no.

Instead, she says neuroscientists who study altruism believe that selflessness is actually hard-wired into the human brain. The idea is that individual humans were once so dependent on the group that the species would never have survived without strong impulses to care for the vulnerable and the needy among them. Those impulses still remain with us today, providing the capacity and the drive to put the needs of others before our own.

In fact, in an interview on NPR’s Ted Radio Hour, Marsh said that research shows that human society is becoming more altruistic. And we aren’t the only species that demonstrates altruistic behavior. Rats will save other drowning rats, primates care for one another, and dogs, says Marsh, have been known to care for almost any species you put in front of them.

“The fact that we care about the plight of strangers who live thousands of miles away from us is actually something really remarkable about us,” said Marsh.

Indeed.

So whether this holiday season you give your uncle the last slice of pumpkin pie, pass out holiday meals at a homeless shelter, hold the doors for someone whose arms are loaded with bags, stop to help a stranger in need, or just pick out the perfect gift for someone you care about — know that the best gift of all is the one passed down to you by human evolution.

All those warm and fuzzy feelings are brain chemicals activated by kindness, that are ultimately making you happier and healthier for many holidays to come.