My Friend Has Been A Heavy Alcohol Abuser - Heavy-

My friend has been a heavy alcohol abuser - heavy- and drug abuser (every variety, morphine, acid, weed, ectasy, easily a pack a day smoker...along with a huge amount of angel dust which is pcp i think....)

i have seen a comedy routine in which a parody of a drug abuser which struck me as it mimicked exactly the way he walked back then... very oddly, almost like his feet no longer knew where the floor was (hard to describe) and a weird kind of head jerking ... So whatever drug leads to that is what he was on and he said it had formaldehyde in it.

He is 45 didn't eat properly forever, was diagnosed with thyroid disorder and did nothing about it or says he was (pathological liar who has also claimed he was in emergency but wasn't several times. So this started at 12 with a physically abusive father. 36 yrs.
He spends a great deal of life sleeping.
Of course there are serious consequences but right now he has
suddenly serious stabbing back pain - is it related?

Heat has not helped at all. He does construction work so not sure if his body is finally beginning to break down or if it is related as he often hurts himself.