I think there's also a difference in definitions. If you look at the comments here, there are many mentioning the effects the day after, after that night out with the gang. To me this would qualify as "heavy drinking that night" not just "drinking". So for some "drinking" means getting hammered, for me (and others) it means having a glass with a book in hand. And I see obvious (health) consequences only for one of those.
I think that's because it depends not only how much you drink, but also how often.
For example if you drink 4 beers in one night, you may consider that night as heavy drinking, but you are not heavy drinking in general if you do it once every month or two. You're more of a drinker if you get a glass of wine every night while reading your book.
While it would make sense, I don't think I've seen this distinction either in comments or in studies. They talk about the same amount daily whatever that is.
