The Chinese Version of the Gotland Male Depression Scale (GMDS): Mokken scaling

Objective: Invariant item ordering (IIO) is defined as the extent to which items have the same order for each respondent who completes a scale. IIO is crucial for establishing a scale hierarchy that is replicable across samples; however, no research has demonstrated IIO in the Gotland Male Depression Scale (GMDS). The aim of this study was to determine if an IIO hierarchy of depressive symptoms existed in a clinical sample of men who completed the GMDS. Methods: A convenience sample of 231 men (age: mean (SD) = 46.1 (11.0) yrs) who visited a men's health polyclinic in Taiwan and completed the GMDS. Mokken scale analysis was conducted to evaluate the psychometric properties of the GMDS. Results: All items on the GMDS formed a strong uni-dimensional scale (H=0.592). Except for item #9 (alcohol/drug abuse, or hyperactivity), IIO was found for the remaining 12 items (H^T=0.366). These symptoms reflected the following hierarchy: positive family history (#13), complaining (#12), anxiety (#8), loss of vitality (#10), depressed mood (#11), indecisiveness (#6), aggression (#2), irritability (#5), stress (#1), burn-out (#3), fatigue (#4), and sleep problems (#7). Conclusion: The GMDS is a psychometrically sound measure of depressive symptoms in Taiwanese male outpatients. The GMDS has both cumulative and hierarchical properties.