A number of well-publicized studies have made the case that children raised by gay parents differ little from those reared by heterosexual couples. As appealing as this conclusion may be, says sociologist Mark Regnerus of the University of Texas, Austin, the supporting research has many flaws. For one, the studies focus on outcomes for children and teenagers, while many effects of upbringing aren’t evident until later in life. Also, they rely on the answers of parents, who may not be the most objective sources. Most important, respondents were self-selected rather than chosen at random, and many were the kind one finds in educated and progressive urban environments.

A study he based on a more varied pool of data “reveals far greater diversity in the experience of lesbian motherhood (and to a lesser extent, gay fatherhood) than has been acknowledged or understood,” Regnerus says. He surveyed a nationally representative sample of 3,000 young adults about their health, social behaviors, and relationships. Most had come of age before gay marriage became legal anywhere—the oldest participants had turned 18 in 1990 and the youngest in 2011. More than 200 respondents had at least one parent who had had a same-sex romantic relationship. It was a diverse group: Forty-three percent of those with a lesbian mother were black or Hispanic.

After controlling for a number of factors, including the age, race, and childhood socioeconomic status of the respondents, Regnerus found that adults with a lesbian mother or gay father fared worse than adults raised by married, biological parents. This finding was based on multiple indicators of well-being, including use of public assistance, employment history, presence or absence of depression, and history, if any, of marijuana use. Among the respondents, 28 percent of adults raised by a lesbian mother and 20 percent of adults raised by a gay father were unemployed, for instance, while only eight percent of adults raised by their married biological parents were out of work. Even in comparison to respondents who had stepfamilies, a status that typically results in poorer outcomes for children, adults with a lesbian mother fared worse on about a quarter of the indicators. (Adults who were adopted by strangers as children differed the least from people raised by their married biological parents.)

Critics argue that the Regnerus study doesn’t say much about children being raised by same-sex parents today—only two respondents in the group he surveyed were brought up from birth by a committed same-sex couple. Regnerus allows that the number of people who have reached adulthood after living in a stable gay household is too small at this point to enable meaningful conclusions. Still, he argues that his findings are consistent with other research on families. “If same-sex parents are able to raise children with no differences” from children raised by their married biological parents, Regnerus writes, “it would mean that same-sex couples are able to do something that heterosexual couples in stepparenting, adoptive, and cohabitating contexts have themselves not been able to do—replicate the optimal child-rearing environment of married, biological-parent homes.”