Discuss the mechanistic reasons re: the direction of IQ <-> Alcohol consumption and
Actually I wanna issue a correction here. They should discuss the mechanistic reasons for the SNP → alcohol consumption link. The point of MR is to figure out things about the IQ <-> alcohol consumption causal link without necessarily having good mechanistic knowledge of it. But as Pearl says, if you put no causes in, you get no causes out; in exchange for the IQ <-> alcohol consumption causal link, you must know even more details about the effects of the SNP that you use for estimation.
Actually I wanna issue a correction here. They should discuss the mechanistic reasons for the SNP → alcohol consumption link. The point of MR is to figure out things about the IQ <-> alcohol consumption causal link without necessarily having good mechanistic knowledge of it. But as Pearl says, if you put no causes in, you get no causes out; in exchange for the IQ <-> alcohol consumption causal link, you must know even more details about the effects of the SNP that you use for estimation.