welcome to health care magic
There could be various causes of late onset psychosis-
1) Organic brain injury/trauma/delirium
(But visual hallucinations
are prominent in that case)
(very rare in this age)
Zoloft contains sertraline
which is an antidepressant.
In old age one has to give the dosages somewhat lesser than the adult dosages due to less efficient metabolism
. But in any case, adequate dosage for adequate duration is required. I advise you to discuss all this in detail with the treating doctor for detailed assessment of causes of failure of the treatment. Incresed dosage or changing of medicines is probably required.
Hope it helps
Dr. Gourav Monga