In cases like this, people often assume that mental illness suffices as an explanation instead of demonic possession. The latter explanation is thus viewed as outdated and unnecessary. But that overlooks the possibility that, in many cases, the full explanation would and should involve both. The former, after all, can both facilitate and be reinforced by the latter. To rule that out is simply to rule out the preternatural as a category of reality. That's a philosophical position, not an empirical one. Once one allows a broader empiricism, one can regard as quite possible what the late Dr. M. Scott Peck considered sometimes actual, as recounted in such books as People of the Lie and Glimpses of the Devil.
Needless to say, the American Catholic bishops have very little to say about such things, now or in general. I know there are some who believe as Peck and I do; perhaps they don't want to stimulate fevered imaginations. But in many cases, I am equally certain, it is because they know little and want to know less. Too bad. It's a tremendous loss.