I see headlines against "cry it out" but can't find actual studies

So far I'm only seeing blog posts (albeit from stuff like psychology today) that rail against CIO (particularly Ferber method) and talk about the flaws in the Flinders study that "prove" there are no issues with CIODo you know of actual studies showing Ferber to be harmful to the baby?I'm totally good with CIO and just want my 4+ mo old son to get good rest do we can also get good rest. I just want to make sure if there's an ACTUAL reputable study out there saying CIO kills their brain or something that I respect that. As of right now it feels like everyone crying against CIO is akin to anti vaxxers via /r/Parenting http://ift.tt/2lGzs7Y