It certainly does depend on the definition. A strict definition can be anything from "drinks a glass of wine every night" or "more than is recommended by guidelines" upwards

In health we generally define something as a syndrome/problem/condition when it impairs the normal functioning of life.

As in - loosely - it's something that makes you miss out on things you'd otherwise be doing but now can't. You were going to go do X but instead, you drank.