as written in the Conclusions section:
“So… this is certainly a surprising result, one that I didn’t expect to find when I started exploring the data. And it is impressively robust even when controlling for many confounding factors. As an exercise I tried controlling for many other confounding factors within the survey data beyond those mentioned here, but it was difficult to make the effect shrink and basically impossible to make it disappear.
Correlation is not causation, and we can never be sure that we’ve controlled for all the confounding factors present in a dataset.”