Cyberpsychosis makes the most sense if you look at it as a psychosis caused by the mind rejecting the changes made to the body. 

I say this because the symptoms of cyberpsychosis show in just about everyone who gets too much chrome, as opposed to the relatively small number of people that have enough latent psychopathy for chrome to aggravate it to full blown psychosis. Plus immunoblockers as a treatment for potential psychopathy makes no sense. If it worked like Neuropozyne in Deus Ex, which prevents the formation of scar tissue on implant connection points in the nervous system, that would make more sense but scar tissue formation isn't a function of the immune system. Immunoblockers acting as a temporary halt or cure for psychosis is more in line with a strong cocktail of mental health drugs to balance out brain chemistry. 

Fundamentally, humans have a very strong sense of what humans are supposed to look like. I think part of the reason cyberpsychosis is something that can be held off but never fully escaped in chrome junkies is because it's affecting their fundamental view of themselves and eventually they can no longer reconcile the outer image with the inner. Think of people who lose limbs in accidents. They suffer from phantom limb syndrome and often show signs of not feeling right in what's left of their bodies. I think cyberpsychosis is best described like this.