As a married mom of two, I always find myself reacting a bit defensively to that research.
"I'm happy," I say to myself. I may be stressed, sleep-deprived and sorely in need of "me" time, but I am very satisfied with my life. Isn't it possible that I could be just as happy as someone without kids -- even if they have more time to sleep and take care of themselves?
According to two recent studies, the answer might be yes and no.
A report by Princeton University and Stony Brook University published in the Proceedings of the National Academy of Science
found "very little difference" between the life satisfaction of parents and people without kids, once other factors -- such as income, education, religion and health -- were factored out, said Arthur Stone, one of the study's co-authors.
People with kids living at home tend to have more money and are more highly educated, more religious and in better health, said Stone, a professor of psychiatry and psychology at Stony Brook University. "All of those are factors that go along with people having better life evaluations."
Once those factors were statistically removed, the study found no difference in how satisfied the two groups felt about their lives.
Stone said in an interview that similarities in reported happiness among parents and the child-free, especially in developed countries like the United States, can be chalked up to priorities, specifically whether a person chooses to have kids.
"I choose an orange because I like oranges. You choose an apple because you like apples. There's no reason to think that your experiences should be any better than mine," said Stone. "The orange is different than the apples. Having kids is different than not having kids. It doesn't mean that one is ... intrinsically better."
Sarah Maizes, author of the children's book "On My Way to Bed"
and a mom of three in Los Angeles, agrees. "It's like asking who's happier -- people who like pizza or people who like Chinese?" she said on Facebook. "Now what I'd like to know is who lives longer. ... That you can measure!"
The Princeton-Stony Brook study -- which involved an examination of a survey of 1.8 million Americans, including parents between the ages of 34 and 46, conducted by Gallup from 2008 through 2012 -- did find one difference between parents and the childless: Parents tend to experience more highs and lows.
"They have higher highs. They have more joy in their lives, but also they have more stress and negative emotions as well," said Stone.
Adina McGinley, a mom of three who lives outside New York, said that watching children grow "is probably life's greatest joy." At the same time, she said, "Stress over wanting your kids to have good lives can be tapped into at any time, sometimes to an awful degree, and this adds endless strain to marriage."
That strain can lead parents to feel less satisfied with their relationship, according to another study, this one by the Open University in England (PDF).
In that study, which involved surveys of more than 5,000 people in England and in the United States, the authors found childless couples were happier with their relationships and their partners than parents were, and were doing more work on their relationships than parenting couples.
When asked who was the most important person in their lives, mothers said their children and fathers said their partners, the study found.
"(It) may be during those mid-years when people are parenting that there is a shift away from the relationship for women as they focus more on children," said Dr. Jacqui Gabb, one of the study's co-authors.
Gabb, who is a senior lecturer in social policy at the Open University, said this doesn't mean the relationships are not working.
"It just means there is a difference in emphasis and probably partly due to the time pinch," she added. "There just isn't as much time to devote to the relationship."
Jen Bosse, a mom of two who blogs at Defining My Happy,
said on Facebook, "All too often when couples have kids, they begin to deprioritize one another. That's the problem, not the children."
Ironically, according to the Open University study, mothers were "significantly happier with life" than any other group including childless women -- a finding, Gabb says, that can be explained by how mothers said children were No. 1 in their lives.
"If they're the happiest with life but the least content with the level of relationship satisfaction and least happy with partners and least happy with the amount of maintenance (of the relationship), but they're happy with life, then there's got to be something," said Gabb.
What's a parent or a non-parent to make of this latest, somewhat conflicting research?
Perhaps the most actionable finding for our lives comes from the Open University study, aptly titled "Enduring Love? Couple Relationships in the 21st Century."
The authors found that when asked what makes people feel most valued in their relationship, research participants said small acts of kindness.
"It's as little as saying 'I love you,' " said Gabb. "Out of everything in life, (mothers) identified having a cup of tea brought to them in bed as significant."
In the U.S., we might replace that cup of tea with a latte from Starbucks, but we all get the point. Relationships benefit from those everyday gestures.
"We need to think differently about what constitutes relationship work, and we need to think about, if it's those everyday small things that are important to people, then let's think about what those small things might be and start to be more attuned to what's going on in our own relationships," said Gabb.
I think I'll be picking up a latte on my way home tonight!