It's not drug related. I'm pretty sure that the guy has some serious psychological issues.
The problem for him is that he seems to be on the verge of depression almost all the time. He's a snooker perfectionist who seems to consider himself to be completely useless if he's not getting left handed 147 breaks.
One of the best snooker players ever, but he loses focus sometimes. I think it's because his world starts getting darker every time he misses a ball, so he drifts off to try and stop himself from feeling so bad.