The thing about Tiger is that he's kind of like a football player without the concussion problems- he's got so many injuries. So it's natural to think that he uses painkillers to help with all of that, and by pretty common extrapolation, become an addict.
Especially when you crash a car on a pretty slow road when passing a pressure cleaning company.
I don’t think there is much doubt his issues stem more from physical problems versus boredom, depression, stress, etc. I’m not sure what you really can do for someone like him where his body is so beat up.