Honey I don't do substances other than cigarettes because I know I'm not me when I do.
It's that classic riddle
What came first the chicken or the egg?
in other words what came first the DID or the substance?
That's why and what T's are trying to figure out.
What if an alter your not aware of drinks because that's their coping mechanism then the switching /changing of other alters happens faster? Because the substance effects or depresses your conscious state/core/ "normal everyday you" so you can not control what the others/alters/EP's are doing?
That's just a theory I have