Psychological explanation for exorcisms? I'm doing research on alleged testimonies and evidences of the spirit realm. In particular, I've been lately reviewing testimonies and live recordings of exorcisms, some of which I find particularly impressive. I say impressive because in my opinion the exorcisms look quite convincing, and I lack the expertise in psychology and neuroscience to provide a convincing explanation other than assuming that everything is staged (which I wouldn't be able to prove either).
Common patterns are that the allegedly possessed person seems to switch personality (as though the alleged entity's personality is taking over), sometimes the exorcist and the alleged entity establish conversation, sometimes the person starts to &quot;throw up&quot; the alleged entity out of their body right before full deliverance is achieved.
Below some example videos with timestamps to illustrate the point:

Woman named Veronica, is exorcised by Bob Larson ( Video not for kids ).

TESTIMONY TURNS DELIVERANCE

Shocking Powerful Deliverance From Demons

Casting Out False NAR Demons (New Apostolic Reformation Warning)

A demon screamed and came out of a woman at the Eiffel tower and the Police was afraid and left. 

Lady's Voice Turns into a Man's Voice - Exorcist Bob Larson Throws out the Demon!

El poder de Cristo - Sacando legión de demonios #chile #imp #estebanguzman #jesus

LIBERACION DE INFLUENCIA SATANICA- Pastor Juan Carlos Harrigan


What is the psychological explanation for exorcisms?
Google Scholar reveals a substantial quantity of learned research on the topic of exorcisms, of which the items below are but a few:

Ferracuti, S., &amp; Sacco, R. (1996). Dissociative trance disorder: clinical and Rorschach findings in ten persons reporting demon possession and treated by exorcism. Journal of personality assessment, 66(3), 525-539. https://doi.org/10.1207/s15327752jpa6603_4

Ross, C. A., Schroeder, E., &amp; Ness, L. (2013). Dissociation and symptoms of culture-bound syndromes in North America: A preliminary study. Journal of Trauma &amp; Dissociation, 14(2), 224-235. https://doi.org/10.1080/15299732.2013.724338

McNamara, P. (2011). Spirit Possession and Exorcism: History, Psychology, and Neurobiology [2 volumes]: History, Psychology, and Neurobiology. ABC-CLIO.

Henderson, D. J. (1976). Exorcism, possession, and the Dracula cult: A synopsis of object-relations psychology. Bulletin of the Menninger Clinic, 40(6), 603.

Bull, D. L. (2001). A phenomenological model of therapeutic exorcism for dissociative identity disorder. Journal of Psychology and Theology, 29(2), 131-139. https://doi.org/10.1177/009164710102900204

Pfeifer, S. (1994). Belief in demons and exorcism in psychiatric patients in Switzerland. British Journal of Medical Psychology, 67(3), 247-258.  https://doi.org/10.1111/j.2044-8341.1994.tb01794.x

Rosik, C. H. (1997). When discernment fails: The case for outcome studies on exorcism. Journal of Psychology and Theology, 25(3), 354-363. https://doi.org/10.1177/009164719702500304


As for many religious behaviours, exorcism behaviours appear to exist between non-intersecting religious and cultural groups.
A review of the abstracts suggests that involvement in exorcism is considered to be a Dissociative disorder.  The Mayo Clinic also has an interesting article on Dissociative disorder.