Published research employing the New Family Structures Study (NFSS), the ECLS (Early Childhood Longitudinal Study), the US Census (ACS), the Canadian Census, and now the NHIS all reveal a comparable basic narrative, namely, that children who grow up with a married mother and father fare best.

A new study published in the February 2015 issue of the British Journal of Education, Society, and Behavioural Science appears to be the largest yet on the matter of same-sex households and children’s emotional outcomes. It analyzed 512 children of same-sex parents, drawn from a pool of over 207,000 respondents who participated in the (US) National Health Interview Survey (NHIS) at some point between 1997 and 2013.

Results reveal that, on eight out of twelve psychometric measures, the risk of clinical emotional problems, developmental problems, or use of mental health treatment services is nearly double among those with same-sex parents when contrasted with children of opposite-sex parents.

The estimate of serious child emotional problems in children with same-sex parents is 17 percent, compared with 7 percent among opposite-sex parents, after adjusting for age, race, gender, and parent’s education and income.

Rates of ADHD were higher as well—15.5 compared to 7.1 percent. The same is true for learning disabilities: 14.1 vs. 8 percent.

The study’s author, sociologist Paul Sullins, assessed a variety of different hypotheses about the differences, including comparative residential stability, experience of stigma or bullying, parental emotional problems (6.1 percent among same-sex parents vs. 3.4 percent among opposite-sex ones), and biological attachment.

Each of these factors predictably aggravated children’s emotional health, but only the last of these—biological parentage—accounted for nearly all of the variation in emotional problems.