Is There a Demonic Affliction?

Of 1800 callers a year that I get, most of those people have already self diagnosed. So they're not asking me to help them sort out what may be happening in their lives. They already believe they're dealing with the demonic and they're looking for exorcism prayers. But I've always believed that the church would do greater harm if it labels someone is dealing with the demons when there's really a medical or mental health issue.