As someone who spent a good two and a half years of their life studying medical anthropology believe me when I say that I definitely understand the value of having non biomedical practitioners give input on psychological illness. Believe me when I say that I firmly believe on treating a whole person including any and all spiritual beliefs they may hold.

AND

is there potential harm from a religious ritual?

YES. Resoundingly YES. And that is ignoring any possibility that a given individual of loose sanity might respond poorly to a figure of a religious authority declaring them possessed.

When psychological treatment is not pursued or withheld as a direct result of the intervention of a professional such as the one who wrote this article, harm has been done.

Have a chaplain in the hospital. Have a chaplain at the inpatient psych ward. let them practice whatever festive rituals make the patients of the relevant spiritual beliefs feel better.

Do not abandon psychological treatment in favor of exorcism.

One psychologists claims of gnosis does not a demon filled world make. Demons don't suddenly exist because one Catholic with a degree says they do.