Nothing, as long as the parents have a stable relationship, new research finds.
Matching 95 same-sex and 95 different-sex parent households, researchers found that children raised by homosexual parents showed no differences in general health, emotional difficulties, coping or learning behavior compared to children of heterosexual parents.
While the results are consistent with prior research, study co-author Dr. Nanette Gartrell said the new findings also stand out.
"No prior study using a population-based survey has compared family relationships and child outcomes in stable, continuously coupled same-sex and different-sex parent households in which the studied [parents] were with their own biological offspring," said Gartrell. She is a visiting scholar at the Williams Institute of the UCLA School of Law in Los Angeles and the University of Amsterdam.
An estimated 690,000 same-sex couples live in the United States, with about 19 percent of them raising children under age 18, according to 2013 national figures cited by the study authors.
Much research has been done on same-sex parent families, beginning with the so-called "lesbian baby boom" in the 1980s when sperm banks first opened their doors to lesbians, the study authors noted.
Increasing numbers of gay men became fathers after same-sex parent adoption became legal. And modern assisted reproduction techniques and surrogacy arrangements have added to the number of households headed by gay parents, the researchers said.
Gartrell and her colleagues focused on female same-sex couples because of a smaller number of male same-sex couples meeting study criteria. The study focused on households with no history of family instability or transitions such as divorce, separation or adoption, and all the parents had been raising their own biological children, aged 6 to 17, since birth.
Parents from both types of households were matched for characteristics such as age; education level; urban or rural residence; their children's age, race and gender; and whether parents or children were born in the United States or elsewhere.
The study was published in the April issue of the Journal of Developmental & Behavioral Pediatrics.
Results showed no differences in spouse-partner and parent-child relationships regardless of family structure. The only difference between the two types of households was higher "parenting stress" reported among same-sex couples.
Dr. Jack Drescher, a psychiatrist and psychoanalyst in New York City, said the higher parenting stress among lesbian parents is probably due to closer societal scrutiny of them, comparing it to other "minority stress."
"This study is consistent with the literature over the last 30 years, with the overwhelming consensus that kids do better with two parents than one parent, and that there's very little difference in long-term mental health for the kids when they're raised" by either same-sex or different-sex parents, said Drescher. He's also emeritus editor of the Journal of Gay and Lesbian Mental Health.
Drescher and Gartrell agreed that more research is still warranted, including long-term population-based studies exploring children's outcomes when being raised by same- and different-sex parents in less-stable relationships.
"We're still in a place where more research is needed," Drescher said. "But, research is all about how to make people's lives better, not meddle or be busybodies."
The American Psychological Association offers more on same-sex parenting.
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