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In certain cases, many neurological / organic brain disorder including subdural hematoma can produce psychotic symptoms mimicking symptoms of Schizophrenia.
However it is difficult to pinpoint the exact cause in most cases because the psychosis can be a primary illness or can be secondary to brain related issues.
In a elderly patient with a medical illness and who is on multiple medicines, delirium is also a possibility. A patients suffering from delirium also may exhibit Schizophrenic symptoms (psychotic symptoms like hallucinations, delusions).
I hope this helps, please feel free to discuss further if you have any doubts / queries.