That would not be your biggest issue here. These types of spirits could terminate his life. This is why there needs to be a couselling and deliverance team. Not just deliverance. The main emphasis is on the word "team". It is God who draws together a team, each with specific gifts needed for the sake of this man or anyone else's freedom. We know that God [through the Holy Spirit] is the greatest deliverer but he tends to use his people in this way for many reasons....
I think I might have said it in another post....Mental illness spirits can be entrenched in a persons pscyhe.(body, soul,spirit).
There can be layers and layers and layers on each level and each issue has to be addressed separately. Dealt with, repented of or forgiven, agreed upon, then removed [cast out] but only as the Holy Spirit leads. The Holy Spirit may lead differently with each level and each layer.
This can actually takes years but it can also take less according to the persons willingnes to be set free and obedience.
Romans 8:28
28 And we know that God causes all things to work together for good to those who love God, to those who are called according to His purpose.
God is not going to throw you in the deep end. You will find that if he is taking you down this path, he will lead the way. You need to listen to his voice and obey his will. He will open doors to divine appointments, create divine encounters, he will place various Godly people on your path. Spiritual Fathers, teachers, prophets, counsellors, evangelists, healers and so forth.
You will think about this conversation many years down the track in hindsight and think to yourself, Wow! Father, you are just so awesome! Thank you for using me for your Kingdom and your glory!!!
Blessings!