ORTO-15

The ORTO-15 is a fifteen-item self-report measure designed to assess ON symptoms⁽⁷⁾. The questionnaire represents the cognitive (six items, e.g. ‘Do you think that consuming healthy food may improve your appearance?’), clinical (five items, e.g. ‘Does the thought of food worry you for more than 3 h a day?’) and emotional (four items, e.g. ‘Do you feel guilty when transgressing?’) aspects of ON. Items were scored on a four-point scale (never, sometimes, often and always). The scores for each item were summed with composite scores ranging from 15 to 60. Lower overall scores indicated increased ON tendencies. Among studies that have utilised the ORTO-15, internal consistency of the scale (in its multiple variations) has previously been reported to range between α = 0·23 and 0·83^(12,14). In the current sample, internal consistency of the original fifteen-item scale was α = 0·50. Following Barnes and Caltabiano⁽¹⁹⁾, items with negative item–total correlations or no correlation were deleted to increase the scale’s internal consistency (items 1, 2, 8, 9, 13). The internal consistency of the scale consisting of ten items was α = 0·76. This revised ten-item version (ORTO-10) was used in subsequent analyses.