The three-item version of the Satisfaction with Life Scale (SWLS) outperforms various structures of the SWLS: Psychometric investigation among people with and without acquired movement disability

Background Subjective wellbeing (SWB) is an indicator of communities’ welfare, which guides vital health, political, and economic decisions, especially concerning vulnerable groups. Stimulated by growing interest in satisfaction with life as the cognitive component of SWB, this study investigated the psychometrics of Diener’s Satisfaction with Life Scale (SWLS) in a Polish sample of community-dwelling adults (N = 120, 50% females, 50% with acquired movement disability). Methods SWLS structure and measurement invariance were evaluated through confirmatory factor analysis (CFA) and multigroup CFA in the whole sample and disability vs non-disability groups. Criterion validity was tested in a SEM detecting SWLS association with self-efficacy and health locus of control. Results CFA revealed misfit of the unidimensional SWLS. Optimal fit was achieved for two bidimensional structures that correlate residuals (present life satisfaction/past life satisfaction; congruence and achievement/acceptance) and a three-item version comprising present life satisfaction (SWLS-3). The SWLS-3 expressed configural, metric, scalar, and strict invariance across age, gender, and disability status. It exhibited higher reliability (0.81–0.86 vs 0.79–0.84) and item total correlations (0.59–0.82 vs 0.50–0.76) in the whole sample and both groups relative to the SWLS. SWLS/SWLS-3 scores were significantly lower in non-disabled and more educated participants, supporting known-group validity. Their criterion validity was expressed through significant associations with general self-efficacy in both groups, albeit at a greater degree in the disability group, which also demonstrated significant associations with the internality, powerful others, and chance dimensions of health locus of control. Conclusion The psychometrics of the SWLS-3 outperform those of the parent scale. Interventions targeting life satisfaction among people with acquired movement disability may produce optimal results if they tackle the effects of handicap on self-efficacy/health locus of control, especially among less educated individuals.