The first signs of borderline personality disorder usually appear by late childhood. The most common early characteristics are impulsive and reckless behavior. The disorder often fully develops between the ages of 18 and 25. The risk of suicide associated with borderline personality disorder is greatest in the young adult years and gradually decreases with age.⁴

In the adult years, the disorder causes intense emotions, impulsive behaviors, and unstable relationships. Uncontrolled emotions and fear of being abandoned often lead to job losses, failed marriages, and uncompleted education. ³

Frequently, other disorders occur along with borderline personality disorder and also need treatment.

Treatment can be difficult, and often people with borderline personality disorder have difficult relationships with their health professionals. People with the disorder often see others as either "good" or "bad". A shift from one view to the other, called splitting, can occur suddenly in any relationship, for minor reasons.

These changes in feeling often are a source of tension between a person with borderline personality disorder and health professionals. Splitting is also a common source of tension in relationships with friends and family members.

Severe symptoms such as self-destructive and suicidal behavior, irrational thinking, and emotional problems related to relationships may improve as you begin treatment. Some symptoms may last longer, such as feelings of anger or emptiness or abandonment, suspiciousness, and difficulty tolerating being alone.¹

Among people with borderline personality disorder, those who are in their 20s are most likely to have thoughts of suicide, and the risk for completed suicide is highest for people in their 30s.⁸

However, the majority of those with this disorder gain more stable emotions, relationships, and employment during their 30s or 40s. Many people who get treatment for borderline personality disorder do decrease destructive behaviors, often within the first year of treatment.⁴ Around half of those diagnosed with borderline personality disorder no longer have many of the behaviors associated with the disorder after about 10 years of treatment.⁴