Dellusions. To take any precautions?

One of my friend had gone to other Country for edu where he had some smoke and bear. But from that time he started feeling nervous he was not eating, not sleeping n not commu with his family for 1 mnth. he was taken to the hospital and was treated with ETC. After the treatment he ws bought to India when he was quite calm but constantly feeling threatened that someone will harm him. He used to say the ppl outside are not normal and they will harm me. or sometimes like people are fake n doing acting. he used to ask many to his family that will he be alright throughout his life and not be harmed by anyone. He was always a guy who has few frds and nvr fully opens up. His confidence was lost and had some bizarre dellusions. This went on for 4 mths aftrwrds he slowly started shwing progress and now its been almost 6 mnths hes becm normal like b4 with no threat & no delusn. He ws Not on any medicines for 6 mnt. . will he be fine forever or we/his family need to take any precautions??