When you say "residual schizophrenia", do you mean people who are schizophrenic but are on an anti-psychotic? I would think so, as schizophrenia cannot be cured. Schizophrenia is diagnosed by two types of symptoms: positive symptoms and negative symptoms. Positive symptoms are those that you mentioned, such as hallucinations, delusions, and disorganized thinking and/or speech. These can be managed with anti-psychotics. Negative symptoms are the classic apathetic vibe some schizophrenics give out, and a lack of will to communicate with others. The negative symptoms are always there in some form, but actually, the anti-psychotics tend to worsen them. This is because the anti-psychotics work to decrease the amount of dopamine in the brain, as schizophrenia is thought to be caused by an excess of dopamine at post-synaptic neurons. Dopamine is the so-called "pleasure neurotransmitter," and with decreased amounts of dopamine, the schizophrenic patient may lose enjoyment of everyday activities and seem lethargic. The main difference would be that schizophrenics are not actually depressed, but they may lack the ability to feel proper emotions at the proper time. This includes happiness as well as sadness. Hope this helped!