Children raised by lesbian parents fare as well as they would in heterosexual households, new research suggests.

The finding, which comes from a review of essentially all studies on the topic of same-sex parents and the health of their children, helps to tease out politics and science on this highly divisive issue. In general, kids in both heterosexual and lesbian households had similar levels of academic achievement, number of friends and overall well-being.

Whether or not kids from homosexual households are more likely to have a non-heterosexual orientation is still unknown. But if there is a genetic component to sexual orientation, it would make sense that kids born to a lesbian mom, say, would be more likely than other kids to be homosexual, scientists say.

At the end of the day, what matters to kids is far deeper than parents' gender or sexual orientation, the research suggests.

"The family type that is best for children is one that has responsible, committed, stable parenting," said study researcher Judith Stacey of New York University. "Two parents are, on average, better than one, but one really good parent is better than two not-so-good ones."

Here are some highlights of the findings:

  • In a study of nearly 90 teens, half living with female same-sex couples and the others with heterosexual couples, both groups fared similarly in school. Teen boys in same-sex households had grade point averages of about 2.9, compared with 2.65 for their counterparts in heterosexual homes. Teen girls showed similar results, with a 2.8 for same-sex households and 2.9 for girls in heterosexual families.
  • In another study, teens were asked about delinquent activities, such as damaging others' property, shoplifting and getting into fights, in the previous year. Teens in both same-sex and heterosexual households got essentially the same average scores of about 1.8 on a scale from 1 to 10 (with higher scores meaning more delinquent behaviors).
  • A 2008 study comparing 78 lesbian families in the United States with their counterparts (lesbian households) in the Netherlands, showed American kids were more than twice as likely as the Dutch to be teased about their mothers' sexual orientation.

Stacey says she doesn't think kids growing up in lesbian households get teased more than other kids; it's just that when they do get teased, the target is the non-traditional household, rather than some other aspect of their life or identity. (On another note, gay and lesbian teens are more likely than others to get bullied.)

Studies of gay male families are still limited since the phenomenon of male couples choosing to be parents is relatively new, Stacey said. So results on children raised by gay men are not firm.

Equal opportunity parenting

But just because two women seem to be able to parent just as well as a man and a woman doesn't mean that fathers aren't important.

"It's not that men don't matter; it's that men can be just as good as women at parenting," said Karen L. Fingerman of the Child Development & Family Studies at Purdue University, who was not involved in the current study. "The key seems to be that parents have someone who supports them in their parenting (i.e., another parent)."

Fingerman and others aren't surprised by the findings.

"This is an interesting paper, and it doesn't surprise me," Fingerman told LiveScience. "If you think about humans historically and cross-culturally, very few cultures use the model we now consider 'normal' with one woman and one man raising one to three children," Fingerman said. "Humans have evolved to be malleable and adjustable, and a variety of models can meet children's social needs adequately."

Politics and science

The results, however, may surprise various individuals on different sides of the same-sex marriage and parenting debates.

For instance, in a 2003 Pew survey of more than 1,500 American adults, 56 percent agreed that gay marriage would undermine the traditional American family. Even so more than 50 percent agree that gay and lesbian couples can be as good parents as heterosexual couples, with 37 percent disagreeing.

In terms of adoption, about the same number of Americans say they favor adoption by same-sex couples (46 percent) as say they oppose it (48 percent), according to a Pew survey of more than 2,000 individuals conducted in 2008.

Those who oppose same-sex marriage, or civil unions, tout various arguments, one of which involves the harm done to children of same-sex couples, whether due to the lack of a father or mother figure or the promotion of homosexuality, the study researchers say.

"Significant policy decisions have been swayed by the misconception across party lines that children need both a mother and a father," said study researcher Timothy Biblarz, a sociologist at the University of Southern California. "Yet, there is almost no social science research to support this claim. One problem is that proponents of this view routinely ignore research on same-gender parents."

What research there is, though, has been limited by statistics. In the United States, about 4 percent to 5 percent of adults are not heterosexual, Stacey said. And of those who are in relationships, only about 20 percent of same-sex couples are raising children under age 18, according to the 2000 Census. That means sample sizes are inevitably small, leading to study results that are less robust.

Also, to gather data on a reasonable number of same-sex couples raising children, researchers often take what are called convenient samples – they go to sperm banks or other facilities where they know they'll find homosexual parents. "The problem from [a] statistical point of view is that convenient sample studies don't amount to much," said sociologist Michael J. Rosenfeld of Stanford University, adding it's hard to extrapolate the results to the real world.

But his research, which used U.S. Census data and not convenient samples, looked at thousands of kids raised by same-sex parents and found no difference in grade retention (when a kid gets held back in school) after accounting for demographics, such as income.

"Grade retention is a pretty strong predictor of problems later in life including dropping out of high school and mortality," said Rosenfeld, who wasn't involved in the current research.

Children in same-sex households

To amass the most exhaustive and reliable data pool possible, Stacey and Biblarz analyzed all of the research they could dig up, which amounted to more than 80 relevant studies.

In general, they didn't find evidence for differences in parenting abilities between two moms versus a mom and dad raising kids.

"[The research] pretty much shows that almost no study that has been done on this topic has confirmed this common sense assumption that gender is critical or that a father-mother household works better for kids than a same-sex household," said Brian Powell, a sociologist at Indiana University, who also wasn't involved in this review.

Some detractors of same-sex parents contend the children will grow up to be homosexuals or at the very least confused about their sexuality or gender. Research doesn't support that idea, however.

"There really is no evidence that not having a mother or father produces any sort of gender confusion or insecure gender identity," Stacey said. "It's a big mystery where gender dysphoria in children comes from. But almost all transgender or gender non-conforming people have heterosexual parents."

However, to date there aren't any studies that have tracked a large enough set of kids raised by gay or lesbian parents into adulthood to know their eventual sexual orientation and gender identity, the researchers say.

Another concern has been that boys raised without a "father figure" will not have an appropriate model for masculinity. A study from the U.K., however, suggested that 12-year-olds raised by mother-only families (lesbian or heterosexual) scored the same on masculinity factors as sons raised by a mother and a father. Interestingly, though, the mother-only boys also scored higher on femininity scales.

Are mom and dad different?

While there were few substantial differences between heterosexual and homosexual parents, some gender stereotypes were confirmed.

Compared with heterosexual couples, the review showed that on average, two mothers tended to play with their children more and were less likely to use physical discipline (relative to the time spent with kids). And like heterosexual parents, new parenthood among lesbians increased stress and conflict within the couple. Also, lesbian biological mothers typically assumed greater care-giving responsibility than their partners, reflecting inequities also found between mothers and fathers.

"The bottom line is that the science shows that children raised by two same-gender parents do as well on average as children raised by two different-gender parents," Biblarz said. "This is obviously inconsistent with the widespread claim that children must be raised by a mother and a father to do well."

The scientists note they don't expect the results to change minds.

"There's a huge gap between research and popular belief and public policy, and it's hard for people to believe something that goes so against what they deeply think," Stacey told LiveScience, adding, "I can't say I'm very optimistic that people will believe us, but I'm hopeful it will open up conversation."