Background
The aim of this study was to broaden the understanding of the emotional difficulties of borderline personality organization (BPO) by reference to a meta-ability named ‘orientation on the internal world’, here conceptualized as mentalization and mindfulness, in the framework of object relation theory. It was assumed that it is not mentalization “in itself”, but mainly its regulatory function, that is important for BPO.

Participants and procedure
The clinical and control groups (30 individuals each) were examined using The Mental States Task, The Difficulties of Emotion Regulation Scale and The Mindful Attention Awareness Scale.

Results
Individuals with BPO functioned worse than the control group in terms of mentalization, mindfulness, and emotion regulation. The relationship between BPO and the meta-abilities was mediated by emotional dysregulation: total mediation was revealed for one mentalization dimension, and partial mediation was observed for mindfulness.

Conclusions
Orientation on emotional experience and emotional dysregulation are not independent predictors of BPO, but they can be treated as levels in the hierarchical model. Mentalization determines and influences emotion regulation in BPO.