You did mix-up myself and JohnW for the Chapman remarks. No problem.
I try to remember Jim Gordon for his contributions to music, rather than personal life tragedy.
As to the alcoholism, alcohol was indeed his drug of choice for many years after he attempted suicide and also made a "come-back" in 1977-1978.
I do believe that the effects of drinking (he had serious health concerns, doctors warned him his liver would fail) and also withdrawing can have a major kindling effect for the delusions and hallucinations to occur, loss of memory etc. and also perhaps vice-versa with self-medicating. Chicken or egg? He was largely drinking himself to death. I'm not a doctor and don't claim to be an expert, but I am not unfamiliar with the topic.
Jim has been kept imprisoned, more or less, for refusing to take anti-psychotic medications and not staying "on-track".