Over the last 50 years, there have been dramatic changes in social attitudes and legislation toward same-sex relationships.

Within this time frame, many countries have moved from criminalisation of same-sex relations to their robust institutional support – enabling same-sex couples to be formally recognised, marry and adopt children.

Despite these developments, same-sex parenting remains a highly controversial and politicised issue, and one that is tightly intertwined with discussions around same-sex marriage.

Data from the most recent wave of the World Values Survey (Figure 1), a large cross-national survey of public opinion, confirms that support of same-sex parenting is far from unanimous. A sizeable share of the population across multiple countries still believes that same-sex parents are incapable of being as good parents as different-sex parents.

These beliefs are often justified by 'common wisdom' arguments that are rarely backed up by robust empirical evidence.

For example, some commentators maintain that children need both male and female parental role models to thrive, that non-biological parents invest less effort in parenting their children and that children in same-sex-parented families would be subjected to shame and bullying.

However, these beliefs have also been fuelled by questionable academic studies examining the comparative outcomes of children raised by same-sex couples.

Prior research

Mark Regnerus, a professor of sociology at the University of Texas at Austin published a controversial study in 2012 that serves as a cautionary tale about the negative and far-reaching consequences that poor data and unsuitable analytical methods can exert on research findings in this field.

The Regnerus study claimed that people raised by same-sex parents experienced worse health and socioeconomic outcomes in adulthood than people raised by different-sex parents.

Yet subsequent re-analyses of the same data by several leading researchers demonstrated that such associations emerged almost entirely due to misclassification, mismeasurement and other analytic problems.

The damage of the Regnerus study was however done, with its spurious findings receiving intense international media coverage and becoming a 'go-to' resource for activist groups lobbying against same-sex marriage.

Findings like this not only permeated the public debate around same-sex parenting, but were also presented in court in attempts to prevent the introduction of same-sex marriage legislation across American states.

Nevertheless, the Regnerus study constitutes an outlier in the broader literature on same-sex parenting.

A large majority of studies on the topic have found that same-sex parents are able to provide their children with as healthy and nurturing home environments as different-sex parents.

Yet these studies have also been often called into question, with critics pointing out that they are typically based on suboptimal data and methods.

The most common criticism is that these studies tend to rely on 'convenience' samples. These are small and selective samples of same-sex-parented families, who may be approached at LGBTQI+ events or recruited through mailing campaigns.

Critics (rightfully) argue that the outcomes of these families may differ from the outcomes of the broader population of same-sex families, and that this can distort the reliability of the studies and their conclusions.

Our new study

In our study, we were able to move beyond the vast majority of research conducted in this space.

We did this by analysing data covering the full population of children living in the Netherlands to compare the academic outcomes of all children raised by different-sex couples (more than 1.4 million children) with those of all children raised by same-sex couples (3,006 children).

We conducted the study in the Netherlands because it's one of only a few countries in the world that allows researchers to link together life-long anonymised data from multiple population registers, containing high-quality administrative information on children and their families.

Thanks to this data, we were able to statistically account for various pre-existing characteristics that may differ between same-sex and different-sex-parented families—for example, the higher average education attainment of individuals in same-sex couples, or their lower average incomes.

This means that our analyses compared children in same-sex and different-sex-parented families that are similar in all observable characteristics except for their parents' sex.

Our key findings go counter to those reported by Regnerus: children in same-sex-parented families attain higher scores on national standardised tests than children in different-sex-parented families.

Their advantage amounts to 13 per cent of a standard deviation, which is comparable to the advantage associated with both parents being employed as opposed to being out of work.

We also find that children in same-sex-parented families are slightly more likely (1.5 per cent) to graduate from high school, and much more likely (11.2 per cent) to enrol in college than children in different-sex-parented families.

Our results challenge those 'common wisdom' arguments against same-sex parenting, and lend preliminary support to other scholarly perspectives that emphasise the possible benefits of same-sex parenthood.

For example, same-sex parents are likely to face substantive barriers to parenthood (including social scrutiny, greater costs of conceiving a child and legislative hurdles) and overcoming these barriers may strengthen their commitment to parental roles.

Combined with the fact that same-sex couples face minimal odds of becoming parents through accidental pregnancies, this can result in more positive parenting practices in same-sex-parented families.

Implications for other countries

The Netherlands features high levels of public approval of same-sex relations and provides robust legislative protections to sexual minorities.

So, the Dutch institutional context represents a 'best-case scenario' concerning the achievement of children in same-sex-parented families.

Same-sex-parented families in other countries may be subject to environmental hurdles that remain out of the control of parents and may negatively affect their children. These include a lack of access to the social institution of marriage and more profound experiences of stigma and discrimination.

By undertaking our analyses in the Netherlands, we were able to retrieve findings that are more likely to reflect the influence of same-sex parenting itself, and less likely to reflect external influences stemming from non-inclusive institutional environments.

Our findings portray a viable scenario of what could happen in countries with more restrictive institutional environments, should they direct comparable efforts towards the inclusion of sexual minorities.

Altogether, the message stemming from our findings is clear: being raised by same-sex parents bears no independent detrimental effect on children's outcomes.

In fact, in socio-political environments that provide high levels of legislative and public support, children in same-sex-parented families thrive.

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