For me, telling my wife explicitly I was an alcoholic, turned out to be a life saver. I never hid my drinking, yet we were still both beating around the bush ("stress", "just slow down", "but you don't xyz yet!?" from the Book of Endless & Clever Denials...). From that point on it was clear that action needed to be taken, that I had a huge problem.
Even if the partner does not understand the full extent, I think it's a good step to take.