I'm saying 'Credible' here, but with caveats. Let's get the preliminaries out of the way. Read it. The piece does provide some interesting information, particularly given the context. So, by all means, arm yourself with as much knowledge as possible. Secondly, and however, the publishing outlet here has a bit of a checkered history. This is not a knock but merely a statement of fact. Thirdly, a quick scan of other, particularly major, news outlets (for example: no mention of this topic in the New York Times, for one) shows basically no other coverage of this (granted, there may be quite a bit in the days and weeks ahead) study. Lastly, and again, no recommendation against reading the piece. But, perhaps do so with a discerning and weather eye.