June 19, 2012

June 19, 2012 | Issue Brief on Family and Marriage

Impact of Same-Sex Parenting on Children: Evaluating the Research

According to conventional wisdom, research regarding outcomes for children of parents in same-sex relationships shows “no difference.” For example, the American Psychological Association (APA) stated in 2005 that “not a single study has found children of lesbian or gay parents to be disadvantaged in any significant respect relative to children of heterosexual parents.”[1] This conclusion has been cited in the judicial proceedings on the nature of marriage. For example, Judge Vaughn Walker’s decision regarding Proposition 8, California’s constitutional amendment defining marriage, stated: “The research supporting this conclusion is accepted beyond serious debate in the field of developmental psychology.”[2]

However, a number of researchers have pointed out significant methodological problems with the research that would cast doubt on the conclusiveness of the “no difference” findings.[3] Even some researchers supportive of same-sex parenting have acknowledged the significant methodological limitations in the research to date.[4] Examples of the methodological problems are discussed below, as well as a profile of the recently released New Family Structures Study, which has raised the bar on quality of research in this area. Given the magnitude of the policy issues under debate, much more study is needed.

Non-Representative Samples

In order to generalize a set of social scientific evidence to a broader group, the samples upon which the evidence is based should accurately represent the broader group. In a probability sample, every member of the broader group has an equal chance of being selected into the sample, and the selection is random.[5] Non-probability samples, on the other hand, cannot make valid generalizations about the broader group because they do not represent it. These samples “may give us interesting leads, and suggest possible insights, but nothing reliable can be inferred from them outside the individuals studied.”[6]

Convenience Samples

A 2010 article reviewed 44 same-sex parenting studies and noted that only five had probability samples; moreover, only three used a nationally representative sample. However, this same sample used by all three studies contained only 44 children of same-sex parents.[7]

The remaining studies were all based on convenience samples, which are comprised of volunteers recruited through targeted advertisement (e.g., in specific publications), the “snowball” method (when respondents identify additional subjects), and/or an existing group.

Consequently, most of the no-differences findings “describe samples of lesbian families that are disproportionately middle class, White, and highly educated.”[8] For example, a 2012 review of the 59 studies reported in the 2005 APA brief on same-sex parenting “reveals a tendency towards not only non-representative but racially homogeneous samples.”[9] Even studies of donor-inseminated (DI) parenthood “do not know the extent to which the comparatively high socioeconomic status of DI parents studied accurately reflects the demographics of lesbian and gay parenthood generally.”[10]

Moreover, in many studies, even the opposite-sex comparison groups are not representative of their respective populations.[11] Researchers also acknowledge the nearly non-existent research on gay fathers and parents who are bisexual or transgender.[12]

Failure to Reflect Diversity

Emerging demographic data suggest significant diversity among same-sex parents. For example, using the Census Bureau’s 2009 American Community Survey, a 2012 report found that, contrary to popular perception, at the national level, same-sex couples raising children are the most likely to live in southern states, not on the west coast or in the northeast. Moreover, minority same-sex parents and less-educated same-sex parents are more likely to be raising children than are white and more-educated parents.[13]

Small Samples

A 2010 review reported that the “mean number of children of gay or lesbian parents in these studies is 39, and the median is 37.”[14] The two studies that used longitudinal, probability samples identified only 44 children of same-sex parents in a sample of more than 12,000 adolescents and 18 lesbian mothers out of 14,000 mothers in the study, respectively. One was supplemented with 21 mothers through the “snowball,” or referral, strategy.[15]

False Negatives

Small sample sizes increase the likelihood of finding false negatives—that is, concluding that there are no differences when they do in fact exist. Of the 22 studies (out of the 49 reviewed) that had a different-sex comparison group, a 2001 review found only one study that had a sufficiently large sample size, which had 25 percent probability of finding a false negative.

For the remaining 21 studies, the false negative rate ranged from 77 percent to 92 percent.[16] Researchers have also acknowledged that “some of the findings of no differences may miss real differences…because some studies use levels of significance that may be too restrictive for their very small samples.”[17]

Inconsistent or Non-Existent Comparison Groups

To conclude that two groups are different, research needs to compare a study group (e.g., children of same-sex parents) with a comparison group (e.g., children of opposite-sex parents). Ideally, these two groups should be identical except for the characteristic of interest that is being tested—in the case of same-sex parenting, the parents’ sexual orientation or relationship status. However, a surprising number of same-sex parenting studies have no opposite-sex comparison groups.

For example, a 2012 review that evaluated the 59 studies in the 2005 APA report noted that only 33 had comparison groups, of which 13 clearly used single-mothers. In the remaining 20 studies, however, the comparison groups were often vaguely defined, with general references to “mothers” or “couples,” and only in rare cases was the comparison group explicitly defined as opposite-sex intact married families.[18]

Moreover, some studies fail to account for all the significant differences between the study and the comparison groups—e.g., mothers’ age or education level—that might bias the no-differences findings.[19]

Other Methodological Problems

Researchers have noted several other methodological limitations in the research on children of parents in same-sex relationships. They include a variety of measurement issues, such as questionable reliability and validity and potentially biased participant responses (e.g., given by parents) due to social desirability considerations.[20]

In addition, in many studies, participants, and researchers were not blind to the nature of the study, which may have introduced biases during the data collection and processing stages.[21] Furthermore, few studies examined longer-term outcomes, as some effects may not be observable until late adolescence or early adulthood.[22]

New Family Structures Study

In contrast to most studies on children of same-sex parents, a new national study called the New Family Structures Survey (NFSS) offers the most representative picture to date of outcomes for children whose parents had a same-sex relationship.[23] It compares a large, national, random sample of such children with their peers from intact families on 40 outcomes and finds significant disadvantages across many of the outcome areas for children whose parents had a same-sex relationship.[24] The NFSS is a rich data source for quality research on children raised by parents who had same-sex relationships. While the NFSS does not answer every research question, it represents an important contribution to the literature on the issue.

More Study Needed

Better data and theories, greater detail, and more rigorous methods over an extended period of time are needed before a broader understanding can emerge.[25] Today, the issue of children’s welfare in association with same-sex parenting calls for more rigorous research based on large, nationally representative samples.[26] The NFSS is an important contribution in this regard. The need is all the more serious given the magnitude of the policy questions at hand related to the institution of marriage.

Christine C. Kim is Policy Analyst in the Domestic Policy Studies Department at The Heritage Foundation.

About the Author

Christine Kim Policy Analyst
DeVos Center for Religion and Civil Society

Show references in this report

[1]Charlotte Patterson, “Lesbian & Gay Parenting,” American Psychological Association, p. 15, http://www.apa.org/pi/lgbt/resources/parenting-full.pdf (accessed June 8, 2012).

[2]Perry v. Brown, 671 F.3d 1052 (9th Cir. 2012), http://www.sfgate.com/chronicle/acrobat/2010/08/04/Prop-8-Ruling-FINAL.pdf (accessed June 18, 2012).

[3]For example, see Steven Nock, “Affidavit of Steven Lowell Nock,” Halpern v. Attorney General, Ontario Superior Court of Justice, Court File No. No.684/00, 2001, http://marriagelaw.cua.edu/Law/cases/Canada/ontario/halpern/aff_nock.pdf (accessed June 3, 2012); Robert Lerner and Althea K. Nagai, “No Basis: What the Studies Don’t Tell Us About Same-Sex Parenting,” Marriage Law Project, 2001, http://www.marriagewatch.org/publications/nobasis.pdf (accessed June 7, 2012); Walter R. Schumm, “Statistical Requirements for Properly Investing a Null Hypothesis,” Psychological Reports, Vol. 107, No. 3 (2010), pp. 953–971; and Loren Marks, “Same-Sex Parenting and Children’s Outcomes: A Closer Examination of the American Psychological Association’s Brief on Lesbian and Gay Parenting,” Social Science Research, Vol. 41, No. 4 (June 2012), pp. 735–775, http://www.sciencedirect.com/science/article/pii/S0049089X12000580 (accessed June 11, 2012).

[4]See Judith Stacey and Timothy J. Biblarz, “(How) Does the Sexual Orientation of Parents Matter?,” American Sociological Review, Vol. 66, No. 2 (April 2001), pp. 159–183; Ellen C. Perrin and Committee on Psychological Aspects of Child and Family Health, “Technical Report: Coparent or Second-Parent Adoption by Same-Sex Parents,” Pediatrics, Vol. 109, No. 2 (February 2002), pp. 341–344; Norman Anderssen, Christine Amlie, and Erling Andre Ytterøy, “Outcomes for Children with Lesbian or Gay Parents: A Review of Studies from 1978 to 2000,” Scandinavian Journal of Psychology, Vol. 43 (2002), p. 348; Fiona Tasker, “Lesbian Mothers, Gay Fathers, and Their Children: A Review,” Developmental and Behavioral Pediatrics, Vol. 26, No.3 (June 2005), pp. 224–240; William Meezan and Jonathan Rauch, “Gay Marriage, Same-Sex Parenting, and America’s Children,” Future of Children, Vol. 15, No. 2 (Fall 2005), pp. 97–116, http://futureofchildren.org/futureofchildren/publications/docs/15_02_06.pdf (accessed June 8, 2012); Richard E. Redding, “It’s Really About Sex: Same-Sex Marriage, Lesbigay Parenting, and the Psychology of Disgust,” Duke Journal of Gender Law & Policy, Vol. 15, No. 127 (2008), pp.127–192; and Michael J. Rosenfeld, “Nontraditional Families and Childhood Progress Through School,” Demography, Vol. 47, No. 3 (August 2010), pp. 755–775.

[5]Nocks, “Affidavit,” pp. 7–8; and Lerner and Nagai, No Basis, p. 70.

[6]Lerner and Nagai, “No Basis,” p. 69.

[7]Rosenfeld, “Nontraditional Families,” Table S1. Of the 44 studies Rosenfeld reviewed for his 2010 Demography paper, 26 studies were published prior to 2001, 11 were published between 2001 and 2004, and seven were published after 2004.

[8]Timothy J. Biblarz and Evren Savci, “Lesbian, Gay, Bisexual, and Transgender Families,” Journal of Family and Marriage, Vol. 72, No. 3 (June 2012), pp. 482–483.

[9]Marks, “Same-Sex Parenting and Children’s Outcomes,” p. 736.

[10]Stacey and Biblarz, “(How) Does the Sexual Orientation of Parents Matter?,” p. 166.

[11]Lerner and Nagai, “No Basis,” p. 76.

[12]Biblarz and Savci, “Lesbian, Gay, Bisexual, and Transgender Families,” pp. 487, 489, 490.

[13]Gary J. Gates, “Family Formation and Raising Children Among Same-Sex Couples,” National Council on Family Relations, Issue FF51 (January 2012), pp. F2–F3, http://williamsinstitute.law.ucla.edu/wp-content/uploads/Gates-Badgett-NCFR-LGBT-Families-December-2011.pdf (accessed June 6, 2012). However, adoption among same-sex parents displays the opposite trend: White and more-educated same-sex parents are more likely to have adopted.


[15]Meezan and Rauch, “Gay Marriage,” p. 106.

[16]Lerner and Nagai, “No Basis,” p. 103.

[17]Biblarz and Stacey, “Gender of Parents Matter?,” p. 8.

[18]Marks, “Same-Sex Parenting and Children’s Outcomes.”

[19]See Lerner and Nagai, “No Basis,” pp. 26–60.

[20]Meezan and Rauch, “Gay Marriage”; Lerner and Nagai, “No Basis”; Tasker, “Lesbian Mothers”; and Anderssen et al., “Outcomes for Children.” According to Lerner and Nagai, reliability refers to “the extent to which repeated applications of the measure result in the same outcome,” and validity refers to the ability “to replicate a measurement” (pp. 63, 65).

[21]Anderssen et al., “Outcomes for Children”; and Tasker, “Lesbian Mothers.”

[22]Perrin, “Technical Report”; Redding, “It’s Really About Sex”; and Marks, “Same-Sex Parenting and Children’s Outcomes.”

[23]Mark Regnerus, “How Different Are the Adult Children of Parents Who Have Same-Sex Relationships? Findings from the New Family Structures Study,” Social Science Research, Vol. 41, No. 4 (June 2012), pp. 752–770, http://www.sciencedirect.com/science/article/pii/S0049089X12000610 (accessed June 12, 2012). The NFSS contains rich data on young adult children of same-sex parents and is the second largest study, after the Census, with information on these children. Screening over 15,000 young adults, the study identified 236 respondents who reported their parents having had romantic same-sex relationships. Examining 40 outcomes in areas—related to their family and romantic relationships, education, physical and psychological well-being, economic and employment status, substance use, and criminal activity and victimization—it found that, compared to children in traditional intact families, those of mothers who have had a romantic same-sex relationship fared, on average, worse on 24 out of the 40 outcomes, and young adult children of fathers who have had a same-sex relationship fared worse on 19 outcomes. Even after accounting for a number of characteristics, these differences remained.

[24]The study also compares children in adopted, divorced, step-parent, and single-parent families as well as children not residing with any parents. In the comparisons, the study takes into consideration young adult children’s age, gender, race/ethnicity, mother’s education level, perceived childhood household income, experience being bullied as a youth, and state’s legislative gay-friendliness. That is, respondents who are identical on these characteristics are compared.

[25]This is evident in a prior research sequence on the intact family. During the early 1980s, the conventional wisdom among researchers was that children from single-parent families fared just as well as children from two-parent families. By the mid-1990s, however, research based on nationally representative data showed that children raised by both parents tended to have better outcomes than children raised by only one. See Sara McLanahan and Gary Sandefur, Growing Up a Single Parent: What Hurts, What Helps (Cambridge, MA: Harvard University Press, 1994). Indeed, a 2002 Child Trends report concluded that “it is not simply the presence of two parents, as some have assumed, but the presence of two biological parents that seems to support children’s development.” See Kristin Anderson Moore, Susan M. Jekielek, and Carol Emig, “Marriage From a Child’s Perspective: How Does Family Structure Affect Children, and What Can We Do About It?,” Child Trends, June 2002, http://www.childtrends.org/files/marriagerb602.pdf (accessed June 5, 2012). Emphasis in original.

[26]In addition to NFSS, two recent studies have used nationally representative data to examine the outcomes of children raised by parents who have had same-sex relationships. One used the 2000 Census, and the other the Early Childhood Longitudinal Study—Kindergarten cohort. These studies analyzed only elementary and middle-school grade retention and reading and math assessment, respectively. For these studies, see Michael J. Rosenfeld, “Nontraditional Families”; and Daniel Potter, “Same-Sex Parent Families and Children’s Academic Achievement,” Journal of Marriage and Family, Vol. 74, No. 3 (June 2012), pp. 556–571.