But if one is predisposed to alcoholism, they might think, "Why even try to fight it? I'm going to succumb at some point anyway, might as well give up now and just enjoy it."
This is just to say that that sword has two edges.
EDIT: Made it abundantly clear that this is not my own personal fatalistic perspective.
This is clearly not my perspective. I'm just illustrating the opposite viewpoint of the one you espoused for the purpose of reminding you that there is an unhappy alternative viewpoint.
predisposed: make someone liable or inclined to a specified attitude, action, or condition.
Just because you're more inclined to do something, doesn't mean you're likely to do something. See the other comment about a 50% increased likelihood moving someone from 1% to 1.5% risk of succumbing to alcoholism.
That said, a lot of people may make the same mistake and succumb to alcoholism erroneously based on the tests.
What you are saying is so true that it becomes almost irrelevant to the discussion. Or, rather, if people understand what you are saying then the rest of the discussion is moot. So the discussion is premised on the fact that many people don't have enough statistical understanding to consider things through that lens.
Let us assume that the absolute risk is non-negligible, and that the predisposition is also non-negligible. Even then, the way that an individual responds to knowledge of genetic risk is idiosyncratic. Some will fight the predisposition even harder, others will succumb even quicker, still others won't know or care.
Because we are talking about the psychology of the individual, and because people do not understand statistics, much less the difference between absolute and relative risk, the fact that the absolute risk for virtually every disease is very small will not matter when an individual considers the issue psychologically.
This is just to say that that sword has two edges.
EDIT: Made it abundantly clear that this is not my own personal fatalistic perspective.