Theory of mind disturbances in borderline personality disorder: A meta-analysis.

Impairments of theory of mind (ToM) are widely accepted underlying factors of disturbed relatedness in borderline personality disorder (BPD). The aim of this meta-analysis a was to assess the weighted mean effect sizes of ToM performances in BPD compared to healthy controls (HC), and to investigate the effect of demographic variables and comorbidities on the variability of effect sizes across the studies. Seventeen studies involving 585 BPD patients and 501 HC were selected after literature search. Effect sizes for overall ToM, mental state decoding and reasoning, cognitive and affective ToM, and for task types were calculated. BPD patients significantly underperformed HC in overall ToM, mental state reasoning, and cognitive ToM, but had no deficits in mental state decoding. Affective ToM performance was largely task dependent in BPD. Comorbid anxiety disorders had a positive moderating effect on overall and affective ToM in BPD. Our results support the notion that BPD patients' have specific ToM impairments. Further research is necessary to evaluate the role of confounding factors, especially those of clinical comorbidities, neurocognitive functions, and adverse childhood life events. Complex ToM tasks with high contextual demands seem to be the most appropriate tests to assess ToM in patients with BPD.