Optimal measurement model is crucial to identify distinct constructs.

This is a Brief Commentary in response to article-"Steinsbekk, S., Jozefiak, T., Ødegård, R., & Wichstrøm, L. (2009). Impaired parent-reported quality of life in treatment-seeking children with obesity is mediated with high levels of psychopathology. Quality of Life Research, 18(9), 1159-1167. doi: 10.1007/s11136-009-9535-6 ." The commentary states that the investigation of the hypothesis if quality of life and psychopathology are two separate constructs may have been hampered by the use of a suboptimal measurement model.