When I was wildly manic, a pentecostal church I went to had elders that performed an exorcism on me. They also convinced me to go off my meds.
Since then I have encountered a similar attitude of MI being demons citing the passage where Jesus cast out Legion.
I don't know what to make of it all except to tell you I threw up during the exorcism, but was still wildly manic afterwards.
I don't believe that it is a treatment for MI, and I don't believe Jesus means for people to be exorcised the way He did it in the Bible.