I'm not sure it's as difficult as you suggest. It's generally a subjective assessment of the individual concerned: is this thing that I feel compelled to do causing me significant harm? There's no need to attach rigorous measure or external validation to that.
That's part of why it can be contentious; people can declare themselves addicted but one suspects they sometimes do it to avert blame for some related action.
That's part of why it can be contentious; people can declare themselves addicted but one suspects they sometimes do it to avert blame for some related action.