The Internet Addiction Test: Factor structure, measurement invariance, and psychometric properties of a six-item version among Spanish women with eating disorders

Abstract

Abstract Background: Eating disorders and internet addiction are widespread conditions that have considerably increased because of the current lockdown. Their comorbidity is frequently undiscovered, which may increase patients’ distress and hamper recovery. Identifying the constructs of internet addiction may facilitate its detection and management. The Internet Addiction Test is widely used to evaluate internet addiction among students and healthy adults, with less agreement on its dimensional structure.Objectives: To examine the structure of the Internet Addiction Test and its invariance among patients with eating disorders.Methods: In this cross-sectional study, exploratory and confirmatory factor analyses evaluated the structure of the Internet Addiction Test among 123 women with eating disorders (59 women with anorexia nervosa (group 1) and 64 women with other eating disorders (group 2)) recruited from the General University Hospital of Ciudad Real between February and November 2018. Multigroup analysis examined invariance of the Internet Addiction Test across eating disorder groups, and correlation with the Bergen Facebook Addiction Scale examined its criterion validity.Results: One factor explained 83.4%, 74.4%, and 87.4% of the variances in the whole sample, group 1, and group 2, with excellent reliability (coefficient alpha = 0.99, 0.98, and 0.99, respectively). In confirmatory factor analysis, two- and bifactor structures (a general factor with two specific factors: Emotional and cognitive preoccupation; Loss of control and interference with daily life) expressed some satisfactory fit in all groups, but they displayed metric and scalar variance—less tendency of women with anorexia nervosa to endorse items 14, 15, and 16. A 12-item version expressed a better fit. However, the six-item Internet Addiction Test expressed the best fit, along with configural and metric invariance across groups, and excellent reliability (coefficient alpha = 0.97, 0.95, and 0.98, respectively). The criterion validity of the Internet Addiction Test, the12-item version, and our six-item version was confirmed by strong positive correlations with the Bergen Facebook Addiction Scale (r = 0.906, 0.883, and 0.878, respectively).Conclusion: The Internet Addiction Test is a unidimensional or bidimensional measure. The six-item version expresses better fit, less variance, and comparable reliability and criterion validity to the Internet Addiction Test and the 12-item version. Its brevity allows test batteries to include several measures. Scalar variance implies that differences in the properties of the Internet Addiction Test across eating disorder groups may cause statistical differences in group means, which should be considered when conducting interventional studies. Further investigations are intensely needed.