Previous research has suggested potential phenotypic similarities between autism and borderline personality disorder (BPD). We aimed to identify overlapping and differentiating characteristics of the two diagnostic groups in women and people assigned female at birth (PAFAB). Women and PAFAB with an autism diagnosis (n = 51) or a BPD diagnosis (n = 51), who had few or subclinical traits of the comparator diagnosis, completed a range of self-report questionnaires. Emotional reactivity, emotional dysregulation, identity disruption, difficulties being alone and rejection sensitivity were significantly more characteristic of BPD-diagnosed participants, with identity disruption representing the biggest difference from autistic participants (d = -1.36, 95% confidence interval CI = -1.79, -0.92). Autistic participants scored significantly more highly on measures of sensory processing, social cognition and behaviour, preference for sameness and repetitive motor behaviour, with sensory processing representing the biggest difference from BPD-diagnosed participants (d = 1.19, 95% CI = 0.76, 1.60). Group differences in social cognition, social camouflaging, identity disruption, impulsivity and coping with being alone, together correctly classified 95.1% of participants (area under the curve AUC = 0.98). However, comparison with measure scores in previous research suggests more complex phenotypic similarities, whereby autistic individuals may show more BPD-aligned characteristics than the general population and vice versa.Lay AbstractAutism can look similar to borderline personality disorder (BPD), leading to misdiagnosis. For example, both diagnostic groups may experience difficulties in regulating their emotions. To improve diagnosis, we wanted to understand similarities and differences between autism and BPD in adult women and people assigned female at birth (PAFAB). We asked two groups of people to complete online questionnaires: (1) 51 women/PAFAB with an autism diagnosis, who do not meet diagnostic criteria for BPD and (2) 51 women/PAFAB diagnosed with and meeting diagnostic criteria for BPD, who are not autistic. The questionnaires asked participants how they experience their emotions, how they interact and relate with other people, how they experience their identity and self-concept, how they react to sensory input, for example, sounds and smells, and how they use repetitive movements, as well as their preferences for sticking to familiar ways of doing things. We found more differences than we expected between autistic people and people meeting diagnostic criteria for BPD. For example, autistic people described being more sensitive to sensory input, described 'masking' more during social interactions and described more challenges in understanding the social behaviour of non-autistic people, compared to people meeting diagnostic criteria for BPD. People meeting diagnostic criteria for BPD described more difficulties with emotion regulation and with their sense of self ('knowing who I am'), were more likely to behave impulsively and found being on their own more difficult, compared to autistic people. Clinicians, and people with a BPD diagnosis who think they may be autistic, can use these findings to better understand the differences between the two diagnoses. Even though we found lots of differences, it is still likely that autistic people experience more similarities with BPD than non-autistic people do and vice versa.
Barnicot et al. (Thu,) studied this question.