For those who arent aware, this entire field is largely pseudoscience; though this paper goes out of its way to be fairly sincere in its modelling, it's still just nonesense methodologically. The correlation coefficient is not a measure of correlation, but of co-linearity, and coefficients the entire system of computing correlation coefficients is bunk if the data is nonlinear. Almost all interesting phenomena outsid…
Nobody who is in the know and actually is skeptical of this branch of work (ie. people like Sasha Gusev) thinks it is as useless as you are making it out to be.
Adoption studies produce causality and even the GWAS (genome-wide association studies) stuff, while not necessarily causal, is pretty interesting.