It's my understanding that one of the reasons there are so many alcohol-related problems on Indian reservations, aside from the enzyme thing mentioned above, is that there is also a very high rate of fetal alcohol syndrome, which was first identified in the 1970's, I think. People withis problem often seem pretty normal, if not too brilliant, but in fact have some major deficits in areas like judgement and understanding. On standard IQ tests they tend to come out at "low normal", but that has nothing to do with the way they actually function in the world. Check out Michael Dorris' book "The Broken Cord," about his adopted son, who had fetal alcohol syndrome. It was also done as a TV movie.