Affective and cognitive theory of mind abilities in youth with borderline personality disorder or major depressive disorder

Abstract Background Theory of mind (ToM) is an important social cognitive ability that has been investigated in BPD, with inconsistent findings indicating impaired, comparable, and enhanced ToM in BPD. This study aimed to clarify and extend previous findings by investigating affective and cognitive ToM abilities in youth early in the course of BPD, by including a clinical comparison group of youth with major depressive disorder (MDD). Methods Female participants aged 15–24 years diagnosed with BPD (n = 41) or MDD (n = 37) completed the Reading the Mind in the Eyes Test (RMET) and Happe’s Cartoon Task, measures of affective and cognitive dimensions of ToM, respectively. Results The BPD group performed significantly worse than the MDD group on the affective ToM task, even after controlling for age, intelligence and depressive symptoms. Results for cognitive ToM were not significantly different. Conclusions Finding of poorer performance on a measure of affective ToM, in BPD youth, relative to youth with MDD early in the course of BPD suggest a developmental failure of sociocognitive abilities needed for mentalising and which are theorised as giving rise to core features of BPD. Future research should employ more naturalistic paradigms to study social cognition and should assess individuals even earlier in the course of BPD.