Correct. Mental illness is ultimately a spiritual problem.
Man is a tripartite being -- body, soul, and spirit. The spirit is dead in all human beings until they receive the gift of the Holy Spirit and are born again. However the soul is the seat of the mind, the will, and the emotions. And there is no remedy for the soul per se, since that is also where "the flesh" (sin nature) resides.
It is the spirit which needs to be *quickened* or brought to life by the Holy Spirit, since the spirit communicates with God and understands spiritual things. And it is only those who have the indwelling Holy Spirit who can have God's power working within them.
Mental illness specialists are compelled to keep everything on a secular and non-spiritual plane, therefore they cannot and will not discuss the power of the Holy Spirit (who is God). Therefore they have no *cure* for mental illness, so they turn to drugs for mind alteration (which is generally more harmful than beneficial).
There is also a close connection between mental illness and demon-possession, and once again psychotherapists have no remedy for this spiritual problem. But the Lord Jesus Christ does have a divine remedy, as seen in Scripture.
And they come to Jesus, and see him that was possessed with the devil, and had the legion, sitting, and clothed, and in his right mind: and they were afraid... And when he [Christ] was come into the ship, he that had been possessed with the devil prayed him [Christ] that he might be with him [Christ]. Howbeit Jesus suffered him not, but saith unto him, Go home to thy friends, and tell them how great things the Lord hath done for thee, and hath had compassion on thee. (Mark 5:15,18,29 KJB)