The Effect of Psychological Distress on Measurement Invariance in Measures of Mental Wellbeing

A growing literature supports the expansion of mental health assessment to include indicators of mental wellbeing; however, the concurrent use of measures of wellbeing and distress introduces potential sources of measurement error. The current study examines whether the mental health continuum short form is invariant to the level of participants' psychological distress. Measurement invariance testing was conducted within an Australian population (n = 8406) who participated in an online survey. The depression anxiety stress scale was used to construct a non-distressed group (n = 6420) and a severe-distress group (n = 1968). Results showed that metric invariance was not observed, as item loadings on the latent variables were significantly different between the groups. This signifies that wellbeing items may be interpreted and valued differently by distressed and non-distressed individuals. Metric non-invariance indicates that total and subscale scores may not be equivalent, and caution is required when making comparisons between these groups.