Ask the vast majority of American parents, and they will tell you that having kids has made them happier.

The problem with this claim, as common as it is, is that research suggests it just isn’t true. People who have kids in the United States and in many countries around the world report being less happy than people who don’t have kids. Being a parent gives people a sense of purpose and meaning, as well as lifelong social connections. But for some reason, it doesn’t appear to bring American parents more happiness.

Now, new research has shed light on why this might be. In research that will be published in the American Journal of Sociology in September, Jennifer Glass of the University of Texas, Robin Simon of Wake Forest University and Matthew Andersson of Baylor University looked at an expansive data set from 22 European and English-speaking countries to find out how and why parents and non-parents in individual countries rate their happiness.

“The cultural stories about parenthood are that it’s wonderful, children are great, it’s the best thing that happens to us. So why do we actually see these gaps? That’s what motivated the research,” says Glass.

The key to their findings is that not every country experiences a “parenting happiness gap” like the United States does. On average, an American parent reports being 12 percent unhappier than a non-parent in America – the biggest gap in the 22 countries the researchers looked at, followed distantly by Ireland. In 12 other countries, non-parents also described themselves as happier than parents. However, in eight countries – Portugal, Hungary, Spain, Norway, Sweden, Finland, France and Russia – parents actually reported being happier than non-parents.

The researchers examined the differences among these countries to figure out what might be causing the happiness gap. They conclude that U.S. policies – or, more accurately, the lack of them – are likely to be the fundamental cause, by increasing the cost and the amount of stress and anxiety that parents feel.

The United States provides minimal assistance to parents, including paid parental leave, mandatory paid sick and vacation days, subsidized child care, and work schedule flexibility, they say. And parenthood is also unusually expensive in the United States, due to the high cost of private education and a lack of public subsidies for childcare. In 2012, the U.S. Department of Agriculture estimated that a middle-income American family is likely to spend $234,900 to raise a child born in 2011 to age 17. If the kid goes to college, that figure may double.

In contrast, countries like Norway, Sweden, Finland and France have extensive social safety nets and supportive family policies, Glass says. Russia and Hungary continue to maintain certain Soviet-era policies that take care of families. In Portugal and Spain, extended family networks tend to help take care of kids. And all of these countries have more extensive policies to support working families than the United States, Glass said.

“What we found was astonishing,” the researchers write in a briefing that explains their findings. “The negative effects of parenthood on happiness were entirely explained by the presence or absence of social policies allowing parents to better combine paid work with family obligations.”

The two policies that explained the most variation in happiness within a country were the cost of care for the average 2-year-old as a percent of wages, and the total number of paid sick and vacation days mandated by law. Compared with these two policies, paid parental leave had a much smaller, though still observable, effect on the happiness gap.

The researchers also found that the presence of family-friendly policies didn’t appear to decrease the happiness of non-parents in those countries –for example, by increasing their tax dollars or work hours.

The researchers caution that their findings don’t mean that American parents are less happy than other parents around the world, as some media outlets have reported. The United States actually ranks second overall on the list in terms of happiness, behind New Zealand and before Denmark. What their findings mean is that American parents and non-parents report the biggest relative difference in happiness among the countries they studied.

Comparing happiness around the world can be a difficult task, the researchers say, because concepts of happiness tend to differ among cultures. So the researchers stick to examining the difference in the happiness reported by parents and non-parents in the same country, saying this measure of “the relative effects of parenting” should help them identify exactly what factors contribute to parental stress.

American parents tend to feel that the challenges they face when raising kids are more of an individual burden than a social problem, Glass says – that if only they were more organized, or if they had more energy, they could do a better job at balancing family and work.

Instead, they should recognize that what they’re experiencing may be part of a bigger social issue.

“We have rugged individualism in the U.S. that makes parents feel that others are coping better than they are. But that’s not the case,” she says. “We know that these problems have been endemic for decades now, and we’ve watched the maternal employment rate in the U.S. steadily erode relative to other countries.”

The good news, the researchers say, is that there is nothing inevitable about the parental happiness gap.

And there may be some relatively achievable solutions for improving the happiness of American parents – like subsidizing childcare, or expanding access to paid vacation and sick leave.

Some of these changes are already happening at a city and state level. This year, California boosted family leave benefits, while cities such as Chicago and San Diego established paid sick leave.

But many Americans continue to juggle kids and a job without these safety nets.

“I think that most parents are completely happy with the fact that they had children and can’t imagine not having those children in their lives,” says Glass. “But loving your children and feeling devoted to them is not the same thing as having a stress-free experience.”