Dimensionality and Psychometric Properties of the Emotions-Affect Systems ELicitation (EASEL-3) in Fibromyalgia and the General Population: A Cross-Cultural Study.

Objective: Despite the growing acceptance and use of the evolutionary tripartite model of affect regulation, the lack of a suitable instrument capable of gauging the activation of the threat, drive and soothing systems hinders further advances. The aim of this study was to preliminarily validate the Emotions-Affect Systems ELicitation (EASEL-3)-a novel index used to estimate the activation of the three affect regulation systems. Evaluated were the assessment of its dimensionality, measurement invariance, psychometric properties and construct and nomological validity.

Method: An international sample of people with fibromyalgia (N = 2033, 94% women) and controls (i.e., people without the disease; N = 463, 71% women) completed the EASEL-3 and clinical symptoms measures. A subsample of people with fibromyalgia (n = 162) completed additional measures of threat (behavioural inhibition, rumination), drive (behavioural activation) and soothing-related constructs (compassionate self-responding, social safeness).

Results: Confirmatory analyses supported a three-factor solution (χ(206) = 2322.236, p < 0.001; CFI = 0.877; TLI = 0.862; RMSEA = 0.071, SRMR = 0.052 for fibromyalgia and χ(206) = 726.838, p < 0.001; CFI = 0.870; TLI = 0.855; RMSEA = 0.074, SRMR = 0.061 for controls) that was found to be partially invariant between groups (ΔCFI, ΔRMSEA and ΔSRMR within the recommended values except for ΔCFI > 0.010 in scalar invariance). Reliability ranged from acceptable to excellent (Cronbach's α = 0.78-0.92). Mean comparison analyses showed that the EASEL-3 profile of people with fibromyalgia significantly differed from that of controls, with the former experiencing a greater threat system activation score and lower drive and soothing system activation scores (all p < 0.001). The EASEL-3 was moderate-to-strongly associated with theoretically related constructs and clinical symptoms. The soothing system activation score moderated the relationship between the threat system activation score and fibromyalgia-like symptoms but not somatic or depressive symptoms. A weaker association between threat activation scores and fibromyalgia-like symptoms was observed with higher soothing system activation scores.

Conclusion And Discussion: Findings support the three-dimensional structure of the EASEL-3, its reliability, temporal stability and adequate nomological and construct validity. Results suggest that the EASEL-3 is a psychometrically sound measure to assess the evolutionary tripartite model of affect through discrete emotions both in fibromyalgia and general populations and to examine how threat, soothing and drive system activation scores differ across populations and may affect symptoms. Future avenues for research are discussed.