There is a major error in the researchers' Letter in JAMA right at the beginning.  But first I commend its authors for recognising that autism can "result in substantial burden for individuals, families, and society", when certain loud voices are denying this.  
The researchers' serious error is the notion that there is a "disorder", indeed "serious disorder", routinely referred to as "Autism Spectrum Disorder".  In reality, there is not the slightest evidence that autism (as manifested in the Autistic Syndrome) is a "disorder".  Sure there is evidence that it can be caused by a disorder, that it can involve disorder, and can sometime be severely disabling.  But none of the is evidence that it is a disorder per se.  And all the evidence actually indicates it is Not a disorder, as is explained in full in Chapter 2 at www.pseudoexpertise.com .  
There is a serious disorder of the academic system whereby once a number of qualified "experts" repeat a pseudo-scientific myth sufficiently it then becomes a presumed "fact" mindlessly parrotted thereafter as supposedly proven "science".   Researchers who don't even understand the basics of what autism "is" have little chance of ever understanding what causes it.