Here is Slash's interview with Variety- https://variety.com/2018/music/news/slash-guns-n-roses-chester-bennington-unreleased-song-1202905755/
Slash admits that if he hadn't been sober for more than a decade, there's no way he could be out on the road now with Guns n' Roses.
The guitarist tells Variety, “I would bet my bottom dollar if I was still carrying the same habit I had 12 years ago, there’s no way I could cope with [the shows]. It would be too physically and mentally difficult. There’s something to be said for a sense of clarity. It’s funny, 'cause dope is such an insidious thing."
Slash adds that he's been impressed at how Keith Richards kept his band, The Rolling Stones, together even with all the various drug issues. “I think he was the main guy who seemed to always have that rule in his head [where] you have to keep the band together, no matter what anybody else did, even himself. No matter hell or high water, you keep it together. But there was a point with Guns where there was so much outside influence that I just couldn’t see around it. I couldn’t see how you went about fixing it."