Parents intuitively know that their children’s friendships are important. They want them to learn how to be a good friend and to maintain solid friendships because we know these skills are critical to lifelong happiness.

But those relationships might be even more crucial than we thought.

A new book by Lydia Denworth, “Friendship: The Evolution, Biology and Extraordinary Power of Life’s Fundamental Bond,” explains the connection between social relationships and personal health. Interactions with friends help lower stress, keep our brains healthy, improve cardiovascular functioning and immune systems, and help us live longer.

Denworth explains the emerging science on how and why friendship literally changes our brains and bodies.

“Over the last few decades, evidence has piled up to show that our relationships, including friendships, affect our health at a much deeper level -- tweaking not just our psychology and motivation, but the function and structure of our organs and cells,” she writes.

It turns out that friendships are just as essential to staying healthy as diet, exercise and sleep. While this takeaway may not come as a big surprise to many, social relationships don’t figure into parenting and education decisions at the level they deserve.

Denworth said researching the book affected the way she parents her own children. She reprioritized the time her adolescent children wanted to spend with friends, better understood the depths of their emotions around friendships, relaxed about the hours her son spent playing video games with a buddy during their summer break, and rethought her reluctance on sleepovers. She also relaxed about social media use: Research finds it’s not necessarily as detrimental as originally thought, and can be used in productive ways.

“There’s a balancing act (for parents) of not over-inserting (friends) in kids’ social lives, but understanding that their social lives are hugely important for their lifelong health and happiness, and that these are skills that must be polished,” she said.

When children are younger, parents can take a more active role in arranging play dates, checking in with teachers if their child seems to be struggling socially, and encouraging positive social interactions. Similarly, schools can be more proactive when children are young. They can incorporate tools like a recess “buddy bench,” where children can find playmates when they need one.

They can also help guide young children to better understand social cues when asking to join in a game.

It’s not about being the most popular kid, Denworth said. She cites research that found that, for a child being bullied, having even a single friend provides an emotional buffer and support.

But facilitating friendship becomes trickier when children are older and averse to social engineering by adults.

When children move to middle school, it’s normal for them to experience significant turnover in their circle of friends, she said. Parents can empower their children with this knowledge as they go through this transition, and reassure them it’s normal to discover new friendships. She cites a study of middle schoolers in which two-thirds of sixth-graders changed friendships between the fall and spring of their first year of middle school.

Schools ought to provide robust support for affinity groups and clubs. These encourage social ties and give students the opportunity to make new friends and create a sense of belonging, at a time when children are struggling to create their own identities. Children do better in school when they collaborate with friends.

The public perception is that loneliness increases as people age, but Denworth found research that indicates that young people experience the most loneliness. Given the amount of attention schools and parents pay to preventing bullying, it makes sense to pay just as much attention to fostering friendships.

Friendship is much more than an emotional bonus; it’s a biological imperative.

We ought to treat it as such.

SLAM!

One of the boys had done it again: run upstairs and slammed the bedroom door behind him.

Parents Kenny and Sam Evers decided this was enough. They were tired of reminding their sons Zach, 11, and Tyler, 9, to stop making so much noise with that door.

So Kenny calmly walked upstairs and took the door off the hinges. He and Sam had threatened to do it before, but their words clearly hadn’t sunk in. Their older son, Gavin, 13, never had a problem closing his bedroom door quietly, but the slamming had become a habit with the younger boys, and it often woke the toddler, Bella.

Initially, Zach shrugged off the missing door.

“Oh, I don’t care,” he said to his father.

A couple of days later, he told his dad that it was kind of annoying not to have a door.

“I bet,” Kenny said. “Do you want it back?”

“Nope,” his son replied.

A couple of more days passed, and Zach came back with another request: “Can I put up a sheet where my door was?”

“Well, you can’t slam a sheet, so go ahead,” said Kenny.

Within a few more days, the boys had had enough: “Can we please have the door back? We will never slam it again.”

The door went back up a couple of months ago, and the lesson seems to have stuck, their parents say. It’s a punishment that’s been around for generations, and many parents swear by its effectiveness.

I reached out to Katherine Reynolds Lewis, parent educator and author of “The Good News About Bad Behavior: Why Kids Are Less Disciplined Than Ever -- And What to Do About It,” to get her take on this approach. Reynolds asked me to consider the purpose of discipline. The goal is not just to make kids behave, she said, but to make them active participants in how to get along and live considerately with others.

She cited the “four R’s” that can transform punishment into learning: The consequence should be 1. Related to the action, 2. Revealed in advance, 3. Reasonable in scope and 4. Respectfully delivered.

In this particular case, she suggested the parents could have implemented this approach by asking the children to brainstorm ways to help them remember to stop slamming the door and what possible consequences would be.

“Does anyone have an idea on how to have less door-slamming?” she suggested. “When (children) have a voice and buy in, they see themselves as actors with responsibility ... and that is the goal we want,” Reynolds said.

Some kids will simply respond they will “try harder” to make whatever changes the parent wants. That’s not a good enough answer, Reynolds said. The parent should help the child break down what “trying harder” looks like in action -- small, concrete steps. She advocates “a total change in mindset” about punishment that moves from fixing one problematic behavior to building lifelong social skills through collaboration.

“It’s not that the (punishment) is necessarily bad,” she said. “It’s how you arrive at it.”

This sounds great in theory, and is the type of parenting I aspire to. But sometimes you’re exhausted and just need the door to stop slamming. I get that, too.

It was the Evers’ next move that took the traditional door-off-the-hinges punishment to another level. About an hour after the door was removed, Sam had an idea. They put the door on the coffee table, and she and her husband re-created the lifeboat scene from “Titanic.”

“You can see Zach in the background (of the picture) with a look on his face, ‘That’s our door,’” she said. They also re-created scenes from “Monsters, Inc.,” “Frozen” and “The Parent Trap,” with the door as the pivotal prop.

Even the two who had just lost their door privileges eventually got into the re-enactments, she said. Tyler ran upstairs to bring his father a robe to borrow for the “Monsters, Inc.” scene.

A week later, he closed the door behind him.

Quietly.

Louise Zdellar was 103 this past November, when she fell in her kitchen the day before Thanksgiving.

She refused to push the Life Alert button she wears. She was afraid of being forced to leave her home if her family thought she couldn’t take care of herself. She knew they would be coming the next day to spend the holiday with her.

So, she spent the night on the kitchen floor.

Her family eventually convinced her that she would be safer in a nursing facility.

“I always thought I was going to stay in my home,” she said. “But there comes a point when you have to go.”

Her family gathered recently to celebrate their four February birthdays. Zdellar, who goes by Weezie, turned 104 this month; also celebrating are her daughter, Judy McGrath (turning 73), her granddaughter, Kristen Statler (turning 37) and her great-grandson, Killian Statler, (turning 2).

They sang “Happy Birthday,” and the four of them blew out the candles on the cake together.

Kristen Statler, who hosted the party in her home, said it reminded her of joint birthday celebrations growing up.

Weezie, born in 1916 in south St. Louis, has lived here her entire life. She reflected on the changes she’s seen in her lifetime. She remembers when a lamplighter would illuminate the streetlights in the days when her neighborhood street was made of brick. During Prohibition, she made “home brew” with her father. She went to Roosevelt High School, then transferred to a vocational school. Shell Oil Co. hired her as a messenger girl when she was 16. She would take the streetcar to work downtown. She met her future husband, Peter, at a dance hall when big band dances were the rage.

She became a homemaker, and they raised two children. She remembers how amazing it was when the family first got a television.

“It was a wonderful invention,” she said.

She finally got her driver’s license when she was 52. The officer asked her why she waited so long, and she explained that her family had one car, which her husband drove to work. She was able to walk where she needed in the neighborhood.

Once she started driving, though, she didn’t want to stop. Even at the age of 102, she went by herself to get her license renewed, and still drove her 1993 Ford Tempo to the grocery store and nearby appointments. When she finally gave up her wheels in 2018, the 25-year-old car had 80,000 miles on it.

“I sure miss when I could get in the garage, hop in the car and go to the store,” she said.

At 104, she still has a valid driver’s license.

Weezie has been on her own for quite some time now. Peter died nearly 50 years ago, when he was 61 and she was 55; they were married just shy of 30 years. She says she had a lot of suitors when she was single, but she didn’t go steady with any of them.

“It had to be the real thing,” she said, and that’s what she had with Peter.

“I was happy all the time with him,” she said, and wishes he could have lived to see his grandchildren.

Now, she’s on hospice care with the service where her granddaughter, Kristen, works. If Weezie thinks this might be her last birthday, she doesn’t show it. She poses with her family for numerous photos. She tosses a ball (while sitting in her chair) to her 3-year-old great-granddaughter, who chases after it.

“I’m still here, and He’s letting me keep my wits about me, and that’s important,” she said, referring to God.

Weezie may not have her car or live on her own anymore, but she still has her independent spirit.

After last year’s Thanksgiving dinner, the family brought out Scattergories.

Despite her fall and the night spent on the floor, Weezie won two rounds.