This is scientific malpractice! The most ridiculous confidence interval I've ever seen! 1.02 to 9.7, reported as "tripled", seriously? And of course the data is non-blinded, self-reported survey responses recalling events that occurred many years ago, and the analysis is not preregistered and splits the cohort in an arbitrary way to eke out so-called "statistical significance" (by the slimmest imaginable margin, 1.02 > 1.00, just barely).
How can this dreck be published? Everyone involved should be sanctioned. And everyone who took this headline at face value should seriously reconsider their approach to consuming science news.
Normally when I see a bad study there's like one or two serious problems with methodology, but when I read this through it's almost just every couple of paragraphs that the authors will say something or describe methodology that should be giving the reader pause. From literally the first paragraph in the intro:
> Changes in diagnostic definitions and guidelines and increased testing availability and funding have made major contributions to this increase in diagnosed cases; under the added impacts of changes in dietary, environmental, and other exposures affecting the intrauterine environment, ASD prevalence has reached unprecedented proportions.
Those two sentences contradict each other! You can't just tie them together with a semicolon like one thought implies the other. I'm not even saying that autism cases aren't actually rising at all, but you can't just go "our diagnostic criteria have changed; therefore environmental and dietary exposures are the cause." You have to actually put in the bare-bottom minimal amount of work to describe why you think that diagnostic criteria and social awareness aren't the primary causes, you can't just claim that changing diagnostic criteria itself implies diets are to blame.
It's unsurprising that somebody who would write this way would do bad statistical analysis.