Background: Multidimensional item response theory (MIRT) model provides an ideal foundation to assess psychological properties of a questionnaire designed with multidimensional structure. This study aims to present the first use of MIRT models to investigate psychological properties of GHQ-12.
Methods: A total of 1104 school children parents completed the Persian version of GHQ-12 questionnaire. A MIRT model was applied to model observed scores for each GHQ-12 item as a function of the subject’s latent traits while taking into account the correlation between dimensions of the questionnaire. The goodness of fit indices were reported and items fit were assessed. Individual items were described in detail through item characteristic curves and the amount of information carried by different items were presented using information curves.
Results: The MIRT analysis of the 12 item GHQ successfully demonstrated two factor structure corresponding to psychological distress and social dysfunction. The model showed all items were fitted adequately. Items varied in their discrimination ranged from 0.86 to 2.35 and 1.18 to 2.41 for psychological distress and social dysfunction, respectively. Moreover, item 8 and item 2 provided the least information in psychological distress and social dysfunction dimensions, respectively.
Conclusions: The developed framework to evaluate psychological properties of GHQ-12 can be a suitable alternative to traditional approaches and also unidimensional IRT models which its use have been restricted due to multidimensional structure of the questionnaire.