The battle surrounding exorcisms exists mainly on two related fronts: the huge "exorcism for profit" ministries that have sprung up in the last couple of decades; and the "psychology vs. religion" debate that sprang up with the advent of psychiatry in the 1800s.
Exorcism for Profit
As soon as money enters the picture, the skeptics are going to win some ground. The rise of money-making "exorcism ministries" around the world leads many people who might otherwise reserve judgment to outright reject the validity of the Catholic view of possession and exorcism, even though the exorcisms performed by these unofficial exorcists are not in any way connected to the Catholic Church.
A particularly popular exorcism ministry in the United States, Bob Larson Ministries, televises its weekly conferences. In these mass exorcisms, for which large groups can receive a "family rate" on tickets, Mr. Larson exorcises the demons of an auditorium full of people. Financial donations on top of the ticket price are not required for his services, but they are welcome.
There are always people who will point to profit as evidence of an ulterior motive, especially when you mix profit with the paranormal.
Psychology vs. Religion
Where one person sees possession and pulls out his rite of exorcism, another sees mental illness and pulls out the DSM IV. This is probably the greatest debate surrounding the practice of exorcism: there may be earthly explanations for behavior the Church considers evidence of diabolical possession.
Several psychological disorders, including Tourette syndrome and schizophrenia, can produce the types of effects seen in "possessed" people. People with epilepsy can suddenly go into convulsions when having a seizure; Tourette syndrome causes involuntary movements and vocal outbursts; schizophrenia involves auditory and visual hallucinations, paranoia, delusions and sometimes violent behavior. Psychological issues like low self-esteem and narcissism can cause a person to act out the role of "possessed person" in order to gain attention. In a case where the subject is in fact suffering from mental illness, the Church is doing harm by labeling the person possessed if this prevents the person from seeking out the medical treatment he or she requires.
Cardinal Jorge Arturo Medina Estevez, introducing the New Rite for Exorcisms to the press in 1999, responds to the conflict this way [ref]:
... exorcism is one thing, and psychoanalysis is another. If the exorcist has any doubt about the mental health of the possessed, he should consult an expert ... It often happens that simple people confuse somatic problems with diabolical influence, but not everything can be attributed to the devil.
The ultimate question remains, "Does exorcism help people or harm people?" It is difficult to come by documentation of any outcomes of official Roman Catholic exorcisms, harmful or beneficial. This is by design: According to the official rite, exorcisms are supposed to be low-key -- not necessarily secret, but not performed in public or in front of press representatives -- so that the ritual does not become a "show." Results are not to be published, whether the exorcism is a success or a failure.
There is considerable documentation, however, of the harmful outcomes of exorcisms performed outside the Catholic Church. One widely reported incident took place in June 2005 in Tanacu, Romania. A priest and several nuns in a Romanian Orthodox convent believed that Maricia Irina Cornici, a 23-year-old nun who lived in the convent, was possessed. So they carried out an exorcism ritual: They tied her to a cross, pushed a towel into her mouth and left her alone without food and water. The intent was to drive out the demon inhabiting her body. Cornici died after three days. Officials believe the young woman had schizophrenia.