What does it actually take for a high-functioning addict to finally stop?

Usually the spouse, not the doctor. Kris Kluver, in The Dysfunctional Family Office, describes Ryan's wake-up call directly. Not the doctors. Not the surgeries. His wife sat him down and told him she wasn't going to watch him kill himself. That was the moment. Functional addicts can usually rationalize their way past medical warnings, performance reviews, and even physical decline. What they often can't rationalize past is the person they love being scared. The pattern is consistent across founders who eventually quit. The decisive moment is rarely a clinical intervention. It's a personal one, usually delivered by a spouse, sibling, or grown child who finally refuses to keep pretending. If you're the founder, the work is to actually let the person in. If you're the family member, the work is to deliver the truth without pulling the punch. The conversation is hard. It's also often what saves the person.