You will rarely, if ever, find a study claiming to prove causation. It is nearly impossible to control for all the factors possible outside of a study that can happen in a lab. So while these are only correlations, I think common sense and revelation (i.e. modern and scriptural) can help get us the rest of the way. I'm thinking Mosiah 2:41. While there are likely many factors that contributed to this kids childhood, it is inaccurate to ignore sinful lifestyles or dismiss them simply because you think it judgemental. Regardless of other factors, if this guy's parents had been keeping the commandments it would have prevented the natural consequences of premarital sex and alcoholism. The OP may have overstated how much of a cause these factors were, but to ignore these factors as unimportant is inaccurate as well.