Normative data of the Magical Ideation Scale from childhood to adulthood in an Italian cohort

The assessment of schizotypy allows to identify people at risk to develop psychosis. For this purpose, psychometric tools have been developed, such as the Magical Ideation Scale (MIS). This scale investigates attenuated forms of thought transmission experiences, thought withdrawal and aberrant beliefs, related to positive schizotypy. This study aims at providing an Italian version of the MIS and its normative data in the general population from childhood to adulthood, being the first study evaluating subjects under 17 year-old. The Italian MIS version was translated by three independent operators and administered to 1378 non-clinical participants, stratified into four age groups (i.e., 8-13, 14-17, 18-24 and 25-34). The unidimensionality of the scale was supported, and its internal consistency was satisfactory (i.e., ordinal Cronbach's αs ranging from 0.86 to 0.90 in different age groups), as well as test-retest reliability (i.e., 1-month ICC of 0.82 in a retested sub-sample). Normative data for the age groups were provided. Specific gender and age-related differences in MIS score were found, i.e. females scored higher than males in the 25-34 age group, which in general, as a group, scored lower than all the other age groups. This study provided evidence of reliability for the Italian version of the MIS in childhood and adolescence, for the first time, as well as in adulthood, showing specific gender and age effects in the early adult cohort.