Borderline personality disorder (BPD) is a long-term mental illness. It is a type of cluster B personality disorder. People diagnosed with BPD are often very impulsive, and generally have a low self-esteem. Moods often change quickly. For these reasons, these people often have trouble keeping a stable relationship. Frequently, people with BPD also suffer from other conditions, such as clinical depression or they show self-harming behavior. Treating people with BPD is difficult, and is usually done using a combination of therapy and drugs.