There's also been a real change even in the kind of facial expressions he makes, like this here:
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I'm not sure what even to call that. It's somehow smug and blank at the same time and his eyes look glassy.
His tone also always seems angry and belligerent, not in the being mad to entertain himself and the audience way, but more Ethan Ralphian. Between that and his apparent inability to maintain a train of thought and choices that suggest impaired executive functioning, I really think he's pickled his brain.
Also not sure how often he's doing molly and other substances. There are plenty of weekend warriors who do that with not much harm, but if he's mixing weird shit with alcohol on a regular basis, that has a multiplicatively bad effect.