A post-doc at my lab told me that the non-drinker group include sober alcoholics, something that might cause the non-drinker group to have a higher overall mortality.
Another possible confounding factor is that the amount people drink is correlated to some genetic differences, which might have other health consequences.
I don't drink at all due, among other things, to the fact that alcohol tastes so awful to me that I cannot help involuntarily grimacing after taking a sip of wine, beer, or liquor.
My roommate recently sent me a review article that LW might find interesting:
Personal observation says that LWers tend not to drink very much or often. Perhaps that should change, to the degree suggested by the article?
Full article here.