I know there are some prescription drugs that can reduce hearing, but they're standard drugs like Ibuprofen, if you're old and take lots of them. I think. I've never heard of any illegal drugs having that effect..

As to RSI being psychological... after Googling around a bit I find a handful of (paraphrasing) "RSI may be to some extent influenced by stress", but nothing that it is 'entirely psychological'? Can you cite sources?

Prolonged use of opioids in high doses can cause permanent damage to the inner ear. Rush Limbaugh famously abused oxycontin and that's likely why he had to get cochlear implants.