Thanks for choosing health care magic for posting your query.
From the description that you have given it appears that your son is probably developed a new onset psychotic episode. If there was any predilection to develop psychotic illness, then it precipitates by taking marijuana.
The voices will go away if he takes proper treatment. The treatment will last for say 6-8 months.
, iloperodone are certain drugs that will be useful for him. He should completely abstain from marijuana.
Hope I am able to answer your concerns.
If you have any further query, I would be glad to help you.
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Wish you good health,
Dr. Srikanth Reddy M.D.