There is a dearth of studies that have explored cognitive performance in different grades of spirit possession.

This study was undertaken to investigate two areas: the first was to explore whether there is a difference in demographic characteristics among presently defined grades of spirit possession in Oman: total possession (TP), partial possession (PP) and symbiotic possession (SP) seen in the Omani society. The second was to compare cognitive performance among the different grades of possession. Assessment criteria for these three groups included indices of current nonverbal reasoning ability, attention/concentration and recall, and those measures calling upon executive functioning.

In terms of socio-demographic characteristics, being female, having low education and being in a particular age group are strongly associated with participants classified as TP. In contrast, the SP group endorsed more history of trauma. The three groups showed performance variation in current nonverbal reasoning ability, attention/concentration and recall, and executive functioning, with TP appearing to have poorer performance on these measures compared to PP and SP.

Previous studies have investigated whether spirit possession is a pathological state or a culture-specific idiom of distress. To our knowledge, this is the first study that has examined performances in cognitive measures among different types of possession. The entrance of possession trance disorder and dissociative trance disorder into the psychiatric nomenclature warrants more studies of this nature.

The authors have not supplied their declaration of competing interest.