Which of the following is a key feature of borderline personality disorder?

Instability in interpersonal relationships is a hallmark feature of borderline personality disorder (BPD). Individuals with BPD often experience intense and chaotic relationships characterized by extreme swings between idealization and devaluation of others. They may have a profound fear of abandonment, leading to frantic efforts to avoid real or perceived separation as well as significant challenges in maintaining stable, healthy relationships. This instability is coupled with emotional dysregulation, making interpersonal interactions particularly tumultuous.

The other options do not align with the characteristics of BPD. Excessive self-satisfaction does not relate to the self-image disturbances and feelings of emptiness often experienced by those with the disorder. Consistent emotional stability contradicts the emotional volatility seen in BPD, where individuals often face rapid mood changes. Lastly, high levels of agreeableness do not accurately represent the interpersonal challenges faced by individuals with BPD, who often struggle with conflict and have difficulty maintaining harmonious interactions. Thus, instability in interpersonal relationships is indeed a defining feature of borderline personality disorder.