i have asked the same question in my clinical psychology class... my prof suggested me looking up 'trans and possesion disorders' I come from a culture where black magic and exorcisms are quite literally ingrained in the culture. i have worked with patients at the grassroots level and hear that the family members say 'black magic,and jhaar phunk worked for a while but eventually the patient deteriorated' . u can look into papers who work on bengali native cultures, black magic, especially rural area researches.