Possession and Schizophrenia

There is an interesting article from boingboing on exorcism and schizophrenia, which explains how patients in cultures with a strong belief in spirit possession, who have been possessed, have often been more successfully treated through schizophrenic medications than through exorcism. While this suggests that possession may be some cultures' ways of articulating the kinds of bizarre behaviors exhibited by schizophrenics, the article also cites a case where one of these medically treated possessees was actually seen to be possessed by other people.

So this might be an otherwise unremarkable psychiatric case if it were not for the fact that the prison chaplain, and several of the patient's cellmates, saw the spirit possess the patient as a ghostly mist. The chaplain was convinced this was a genuine case of possession, as had priests from several other faiths who had previously carried out exorcisms on the patient.

This begs the question, if the patient was treated for his belief in spirit possession and his apparent hallucinations as to the reality of the ghost, why were the chaplain and the others not considered to be ill ?

One could argue for mass hallucination, or conversely for some kind of cultural imagination at work, but perhaps it could mean that actual ghosts/spirits may be affected by chemical procedures? Not knowing off hand how medicines like trifluoperazine and clopenthixol work, I'd hazard a guess that whatever neural site/receptor these chemicals effect is also the neural site/receptor ghosts take possession of.