Makes sense. People who are going to adopt usually take their job more seriously and do a better job than most people. Especially when we consider unwanted births at a young age, or single parents with the rest of the population.
I see they adjusted for income/education. However, the study appears to have neglected adjusted for:
a) Unplanned pregnancies/unwanted children
b) Single parenthood
I'd say those are the two major factors that would harm a child's development. Indeed the headline might as well be "Wanted children from intact homes do better than everyone else".
I also note that the while the survey covered 315 parents and 500 children, it appears that the questions were asked only of the parents. Also, the participants were recruited. Without a comparison group of heterosexual couples surveyed under the same conditions by the same surveyors, I'm dubious of the statistical validity of the study, especially insofar as the specific claims being made.
