ABSTRACT
Objectives: The purpose of this exploratory non-randomized controlled study was to determine the acceptance and effectiveness of an 8-week mindfulness-based intervention (MBI) co-designed by a police officer. Methods: A pretest-posttest control group design was followed. Participants (MBI group = 20; control group = 18) answered baseline and post-training self-reported measures. In addition, the weekly emotional state of the MBI group was collected. Paired-samples t-test and analysis of covariance were performed for pre-post within-group and between-group differences, respectively, as well as linear mixed effects analysis of repeated measures for week-by-week data. Results: High acceptance and attendance rates, as well as significant pre-post within-group differences in the MBI group in mindfulness (η 2 = 0.43), self-compassion (η 2 = 0.43), depression (η 2 = 0.54), anxiety (η 2 = 0.46), stress (η 2 = 0.51), difficulties in emotion regulation, sleep quality (η 2 = 0.57), and burnout (η 2 = 0.31-0.47), were identified. Moreover, police officers who underwent the MBI experienced a week by week decrease of anger, disgust, anxiety, sadness, and desire. Finally, after adjusting for pre-test scores, significant between-group differences were found in the way of attending to internal and external experiences (observing mindfulness facet; η p 2 = 0.21), depression symptoms (η p 2 = 0.23), general distress (η p 2 = 0.24), and the degree of physical and psychological exhaustion (personal burnout; η p 2 = 0.20). Conclusions: The preliminary effectiveness of this MBI on psychopathology and quality of life outcomes in Spanish police officers was discussed. Previous evidence regarding the promising use of MBIs in this population was supported.