Muscle Dysmorphic Disorder Inventory (MDDI): Validation of a German version with a focus on gender.

Muscle dysmorphia (MD) is a condition that is characterized by body image disturbance, a drive for muscularity and excessive exercising. It leads to considerable functional impairment. Most previous studies focused on male samples. The study aimed to validate a German version of the Muscle Dysmorphic Disorder Inventory (MDDI) in order to make the instrument available in German speaking countries. We further aimed to explore for gender differences in the MDDI factors (measurement invariance) and to assess the relationship between MD and positive dimensions of body experience as well as exercise dependence. 394 participants (53% females, mean age 24.3 years) took part in an internet-based survey. The three-factor structure of the English version of the MDDI was replicated, independent of gender (multi group CFA; Base model TLI = .961; CFI = .970). Cronbach´s alpha was .81-.84 for the subscales and .75 for the MDDI total score. MD was associated with exercise dependence and negatively correlated with dimensions of positive body experience, which can be considered relevant for satisfying relationships and a positive sense of self: e.g. body contact and sexual fulfillment. Men and women showed differences in two subscales of the MDDI (appearance intolerance, drive for size). Testing for measurement invariance resulted in weak invariance: Equivalent factor structure for men and women, but significantly different loadings and coefficients. No statistically significant difference in the MDDI total score was found. The findings suggest good psychometric properties of the German version of the MDDI. Future studies should address the question of cut-off scores and norms for different samples as well as a possible overlap between MD and eating disorder psychopathology in women.