I do not understand the amount of uninformed objections to the presented results in a number of comments here … you can’t just discount the results of a peer-reviewed study with some generic knee-jerk interjection off the top of your head. Read the original article here. It details which covariates were considered and how they were taken into account. Income bracket, educational background, gender, … all this shit is not new to researchers.

Don’t get me wrong: JAMA Pediatrics being a reputable journal shouldn’t lull you into complacency, but JFC, just because you don’t agree with the findings of a study doesn’t mean you have to dismiss it completely on first glance.