Psychometric validation of the Danish version of the Major Depression Inventory using data from the Lolland-Falster health study (LOFUS).

The MDI is psychometrically valid in homogenous sub populations, but the disclosed evidence of local dependence means that published estimates of its reliability cannot be trusted. The lack of measurement invariance means that the instrument cannot be used to compare individuals or groups unless they are similar in terms of age group and chronic disease status.