Southampton Mindfulness Questionnaire: Confirmatory Factor Analysis and Psychometric Properties Across Portuguese Clinical and Non-clinical Samples

Southampton Mindfulness Questionnaire (SMQ) is one of the available instruments to assess mindfulness and has been described as particularly suited for clinical populations. The original study of the SMQ conceptualized it as having four facets, but yielded a single factor structure. The aim of this study was to confirm the SMQ factor structure and examine its psychometric properties in clinical and non-clinical Portuguese samples. The community sample comprised 243 participants, ranging from 18 to 77 years. Additionally, to assess sensitivity, two distinct samples were used: individuals with meditation experience (n = 30) and a clinical sample (43 individuals with psychosis). Factor structure, reliability, validity, and sensitivity analyses were performed. Confirmatory factor analyses of the SMQ seem to support one overarching mindfulness construct containing four facets, revealing an acceptable fit through a parceling method. Significant correlations were obtained between SMQ and another mindfulness measure, and also with measures of cognitive fusion, and positive and negative affect. Results also indicated significant differences in SMQ non-judging facet between meditators and non-meditators and clinical samples. The results indicate that although the SMQ has shown adequate reliability and validity, some limitations to the measure have been found. Further studies are needed, particularly with clinical samples, to determine how the current SMQ version could be improved and whether it should be revised.