What is a key symptom of borderline personality disorder?

A key symptom of borderline personality disorder is intense emotional instability. Individuals with this disorder often experience significant and rapid changes in their emotional state, which can manifest as feelings of extreme sadness, irritability, or anxiety that may last a few hours to a few days. This emotional volatility is often triggered by interpersonal stressors or perceived abandonment, making relationships particularly challenging.

The fluctuations in mood can lead to impulsive behavior, difficulties in maintaining stable relationships, and self-image issues, as these individuals may swing between idealizing someone and then feeling intense anger or disappointment toward them. Such emotional dysregulation is a central aspect of borderline personality disorder, distinguishing it from other disorders where mood might be more stable.