I was looking this up for a conversation online, and wanted to keep it for future reference.
According to a report by the American Academy of Pediatrics, “A growing body of scientific literature demonstrates that children who grow up with 1 or 2 gay and/or lesbian parents fare as well in emotional, cognitive, social, and sexual functioning as do children whose parents are heterosexual.”
Overview of the research literature by the Australian Psychological Society (pdf):
“As detailed in this review, the family studies literature indicates that it is family processes (such as the quality of parenting and relationships within the family) that contribute to determining children’s well-being and ‘outcomes’, rather than family structures, per se, such as the number, gender, sexuality and co-habitation status of parents. The research indicates that parenting practices and children’s outcomes in families parented by lesbian and gay parents are likely to be at least as favourable as those in families of heterosexual parents, despite the reality that considerable legal discrimination and inequity remain significant challenges for these families.”
Also of interest may be an Amicus Curae brief (pdf) from the American Psychological Association, The California Psychological Association, The American Psychiatric Association, and the American Association for Marriage and Family Therapy, regarding the Perry v. Schwarzenegger case (the challenge against California’s Proposition 8 ban on same-sex marriage):
“The research literature on gay, lesbian, and bisexual parents includes more than two dozen empirical studies. These studies vary in the quality of their samples, research design, measurement methods, and data analysis techniques. However, they are impressively consistent in their failure to identify deficits in parenting abilities or in the development of children raised in a lesbian or gay household. In summarizing the findings from these studies, amici refer to several reviews of empirical literature published in respected, peer-reviewed journals and academic books and empirical studies.”