Schizophrenics are born with the underlying condition which usually manifests as a certain naivety. Full blown psychosis is usually triggered by an extremely stressful event in the teens or twenties. Hence the blame being put on the toxicity directed at him. I would bet a sizable amount that he is downplaying the effect it had on him. That is a fairly typical response for stabilized Schizophrenics.

Lobot's cybernetic implant was an enhancement of his own natural abilities, not a plot device in the aid of a culture that worships disabilities and feelings of inadequacy above all else.