Which are the best questionnaires to longitudinally evaluate mindfulness skills in personality disorders?

Background: Personality disorders (PDs) are severe mental illnesses, characterized by inflexible and enduring response patterns in a broad range of personal and social situations. With the aim of identifying effective and evidence-based interventions, in the last decades we observed a flourishing of the so-called "thirdwave" cognitive-behavioural therapies, where mindfulness appears as relevant factor in promoting individual well-being and treatment response. In this regard, several authors tried to develop new instruments that enable to measure mindfulness skills, such as the Kentucky Inventory of Mindfulness Skills (KIMS), the Five Facet Mindfulness Questionnaire (FFMQ) and the Philadelphia Mindfulness Scale (PHLMS). The aim of this review is to provide new insights about the mindfulness questionnaires currently used in longitudinal studies in PDs by providing a benchmark for future studies evaluating mindfulness changes associated to therapeutic interventions. Methods: In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic search in PubMed was performed. Three reviewers conducted the data extraction. Longitudinal studies on PDs evaluating mindfulness skills through a validated questionnaire were selected. Ten studies met the selection criteria. Results: The majority of the studies reviewed (N=7) detected an increase in mindfulness skills (4 rated with FFMQ, 2 KIMS, and 1 Philadelphia Mindfulness Scale). Finally, from the selected studies mindfulness changes were also associated with clinical amelioration. Limitations: Few studies evaluate male patients and PDs other than borderline personality disorder. Conclusion: Although mindfulness is a complex construct to operationalize, the considered questionnaires emerged as useful instruments for clinicians to detect changes in mindfulness abilities. In particular, currently the FFMQ appears as the most suitable measure.