Borderline personality disorder is a mental illness that severely impacts a person’s ability to manage their emotions. This loss of emotional control can increase impulsivity, affect how a person feels about themselves, and negatively impact their relationships with others. Effective treatments are available that can help people manage the symptoms of borderline personality disorder.

People with borderline personality disorder may experience intense mood swings and feel uncertainty about how they see themselves. Their feelings for others can change quickly, and swing from extreme closeness to extreme dislike. These changing feelings can lead to unstable relationships and emotional pain.

People with borderline personality disorder also tend to view things in extremes, such as all good or all bad. Their interests and values can change quickly, and they may act impulsively or recklessly.

Other signs or symptoms may include:

• Efforts to avoid real or perceived abandonment, such as plunging headfirst into relationships—or ending them just as quickly.
• A pattern of intense and unstable relationships with family, friends, and loved ones.
• A distorted and unstable self-image or sense of self.
• Impulsive and often dangerous behaviors, such as spending sprees, unsafe sex, substance misuse, reckless driving, and binge eating. However, if these behaviors happen mostly during times of elevated mood or energy, they may be symptoms of a mood disorder and not borderline personality disorder.
• Self-harming behavior, such as cutting.
• Recurring thoughts of suicidal behaviors or threats.
• Intense and highly variable moods, with episodes lasting from a few hours to a few days.
• Chronic feelings of emptiness.
• Inappropriate, intense anger or problems controlling anger.
• Feelings of dissociation, such as feeling cut off from oneself, observing oneself from outside one’s body, or feelings of unreality.

Not everyone with borderline personality disorder will experience all of these symptoms. The severity, frequency, and duration of symptoms depend on the person and their illness.

People with borderline personality disorder have a significantly higher rate of self-harming and suicidal behavior than the general population.

Studies suggest that genetic, environmental, and social factors may increase the likelihood of developing borderline personality disorder. These factors may include:

• Family history: People who have a close family member (such as a parent or sibling) with the illness may be more likely to develop borderline personality disorder due to shared genetic factors.
• Brain structure and function: Research shows that people with borderline personality disorder may have structural and functional changes in the brain, especially in areas that control impulses and emotion regulation. However, it is not clear whether these changes led to the disorder or were caused by the disorder.
• Environmental, cultural, and social factors: Many people with borderline personality disorder report having experienced traumatic life events, such as abuse, abandonment, or hardship, during childhood. Others may have experienced unstable, invalidating relationships or conflicts.