How does mindfulness skills training work to improve emotion dysregulation in borderline personality disorder?

Mindfulness skills training is a core component of Dialectical Behavior Therapy and aims to improve emotion dysregulation (ED) in people with Borderline Personality Disorder (BPD). However, the underlying mechanisms of change are not fully understood. A total of 75 BPD outpatients participated in a 10-week mindfulness skills training. Multilevel models with a time-lagged approach were conducted to examine the temporal dynamics between the proposed mechanisms and ED. Decentering, nonjudgment, body awareness and attention awareness as putative mechanisms and ED as outcome were assessed on a session-by-session basis. Greater nonjudgment and body awareness showed within-person effects; participants who reported higher nonjudgement of inner experience and body awareness than their own personal average at a given week showed improvement in ED at the following week. Notably, decentering moderated these associations, such that increased nonjudgment and body awareness predicted improvements in ED more strongly in those participants with high decentering ability. Lastly, a bidirectional relationship between the mechanisms and ED was found; when participants were more emotionally dysregulated than their usual state, they showed less gain in the mechanisms at the following week. Knowing how mindfulness training works is relevant to optimize treatments. Clinicians may use strategies to increase these mechanisms when the goal is to improve emotion regulation difficulties in BPD.