Development and Validation of the Test of Orthorexia Nervosa (TON-17)

Aleksandra M Rogowska,Dominika Ochnik,Aleksandra Kwaśnicka

doi:10.3390/jcm10081637

Aleksandra M Rogowska, Dominika Ochnik + Show 1 more

Open Access

https://doi.org/10.3390/jcm10081637

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Abstract

This study aims to develop and validate a new self-report questionnaire to measure orthorexia nervosa (ON). Based on a current review of the scientific literature and interviews with people at risk of orthorexia, 40 items were selected to test orthorexia nervosa (TON-40). A total sample of 767 individuals (M = 26.49, SD = 9.66, 56.98% women) participated in the study. The exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and composite construct analysis (CCA) were performed to find an appropriate model of sufficient reliability and validity and stable construction. Convergent validation was performed regarding the correlation of the TON-17 with another measure of ON (ORTO-15), eating disorders (the EAT-26 and DEAS), healthy behavior (the HBI), quality of life (the Brief WHOQOL), physical health (the GRSH), anxiety (the GAD-7), depression (the PHQ-9), and obsessive-compulsive disorder (the OCI-R). Gender, Body Mass Index (BMI), and the medical reasons for a restrictive diet were also examined. As a result of the structural analyses, the number of items was reduced from 40 to 17. The best fit indices of the TON-17 were found for the hierarchical bi-factor model, with three lower-order factors (Control of food quality, Fixation of health and healthy diet, and Disorder symptoms) and one general higher-order factor (Orthorexia). According to the 95th percentile method of estimation, the prevalence of ON was 5.5% for the TON-17 total score. The TON-17 scale and subscales showed good psychometric properties, stability, reliability, and construct validity. The TON-17 indicated a positive relationship with the ORTO-15, EAT-26, DEAS, HBI, OCI-R, GAD-7, and PHQ-9. TON-17 can be considered as a useful tool for assessing the risk of ON.

Highlights

The internal item qualities analysis was performed in the total sample (n = 767) to examine properties of items that can be assessed in reference to other items on the scale or in reference to the scale’s summated scores
The item-total correlation is frequently used for reducing the length of self-report questionnaires
The assessment of scale reliability is based on the correlations between the individual items or measurements that make up the scale relative to the variances of the items

Summary

Introduction

Many researchers agree with the above definition, particular approaches to ON vary, highlighting different diagnosis criteria [2], such as weight loss [3], phobic avoidances [4], and the exclusion of food allergies or medical conditions that require restrictive diets [5,6]. No consensus has been found, regarding whether ON should be classified as a single syndrome of an eating disorder or a variance of other syndromes, such as anorexia nervosa (AN), avoidant/restrictive food intake disorder (ARFID), obsessive-compulsive disorder (OCD), obsessive-compulsive personality disorder (OCPD), somatic symptom disorder, illness anxiety disorder, or psychotic spectrum disorders [7,8,9,10,11]

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