One of the main issues that people with borderline personality disorder (BPD) and/or autism spectrum disorder (ASD) experience is that they find emotional and relational interactions challenging.

This article reviews the available literature on the similarities and differences between BPD and ASD, and aims to raise awareness of the complexity of co-morbid presentations. This is important because, if a person’s diagnosis is inaccurate or incomplete, their treatment may be ineffective or inappropriate. The authors provide practical guidelines to assist front-line mental health practitioners in diagnosing BPD and/or ASD, thereby enabling them to develop appropriate and effective management plans. These guidelines were drawn from the available literature and the authors’ experience in clinical practice. When BPD and ASD co-occur, a formulation approach should be used to provide person-centred care, rather than an assessment approach that simply defines the issues a person is experiencing.