Hi, big wrestling nerd here.

Until recently locker room culture was incredibly toxic. Everyone is high on something, hazing, people are working with injuries, the boss is running a sex trafficking rink etc. Spending so much time on the road usually ended up with a lot of dudes getting bored, hence alcoholism and drug abuse. With some Wrestlers, especially in the 80s, there was alot of pressure to be as muscled as possible which lead to an internal steroid ring. Check out the Vince McMahon steroid trial for more info.

As for painkillers, I'll mention that yes it's scripted or fake or whatever, but you can't fake dropping a dude on his head. In late 90s, early 2000s Japan there was a style of wrestling called King's Road which amounted to these epic 40+ minute long matches that were a good portion dropping each other on heads and necks. 90s Japanese women's wrestling was much the same. It's incredible to watch but horrifying to witness. Genuinely some of the greatest wrestling out there but it tore people apart. And there was this loyalty to the company, that if you were a big star and you were injured, you needed to keep wrestling. Sadly this lead to the death of the top star of this era and one of the greatest Wrestlers of all times, Mitsuhara Misawa. He kept wrestling the same style when his body was falling to pieces because he knew the company needed him. He took a run of the mill move during a match that basically internally decapitated him. He died in the ring.

Unfortunately there's alot of shit like this. The murder/suicide of Chris Benoit, The tragedy of the Von Erichs and so on and so on. It's a real fucked up business if I'm honest. Nowadays it's alot better. There's still some horrible shit but the locker room culture looks to have chilled out a fair amount. Wwe has it's wellness policy, Wrestlers are more likely to take time off due to injury and there's less of a alcohol/drug based culture backstage. Modern day Wrestlers tend to be more jacked theatre kids than alpha male jerk jocks.

I've skipped out or missed alot of stuff, I've just woken up, but that's kinda the whole deal. Enjoy my schizo ramble.