He doesn't have to believe he has ALS to believe he needs to control the pain. Pain is bad for the heart, can cause strokes--and believe me, it can affect personality.
Another poster was correct. It can increase blood pressure to dangerous levels if bad enough. My BP hasn't been below 180 in a month
I've been out of my pain meds for a month, and I'm in constant pain --and a total ***** because of it.