Predictive Validity and Response Shift in the Equanimity Scale-16

The predictive validity of the Equanimity Scale-16 (ES-16) has not yet been examined, despite its suggested utility in measuring reduced reactivity and increased experiential acceptance following a mindfulness-based intervention (MBI). In this study, we examined the predictive validity of the ES-16 in a heterogeneous clinical group who underwent a 10-session mindfulness-integrated cognitive behavior therapy (MiCBT) and a general population (control) group. As the advantage of accounting for response shifts in MBIs has been demonstrated but not evaluated on equanimity scales, this study also investigates potential response shifts on the ES-16.

A heterogeneous clinical group (n = 52; 46.2% males, 53.9% females; age 19–67) with one or more mental health conditions undertaking a mindfulness-based intervention (MiCBT) and a control group (n = 67; 43.3% males, 56.7% females, age 18–67) were recruited from the general population via social network platforms. All completed measures of equanimity, depression, anxiety, stress, and five facets of mindfulness at pre-treatment and post-treatment, and pre-treatment ratings were re-scored retrospectively after treatment in order to assess response-shift effects in both clinical and control samples.

As predicted, the clinical group scored the ES-16 significantly lower than the control group at pre-treatment (p < 0.001) and significantly higher than the control group at post-treatment (p < 0.001). A significant interaction between Group and Time was found on all measures (p < 0.001). Follow-up pairwise comparisons detected response-shift effects on all measures in the clinical group, but not in the control group.

The ES-16 was sensitive to improvements from pre- to post-intervention in the clinical group and discriminated clearly between participants with one or more mental health conditions from those in the general population, both at pre- and post-treatment, showing good predictive validity. Response shift was detected on all measures in the clinical group, suggesting that pre-/post-assessment may underestimate the effectiveness of MiCBT, and possibly other MBIs. Results support both the use of the ES-16 in clinical contexts and the utility of retrospective scores to detect and quantify response shift as a measure of increased experiential awareness following an MBI.

This study is not pre-registered.