John F. Clarkin, PhD, is Clinical Professor of Psychology in Psychiatry at Weill Cornell Medical College and Co-Director of the Personality Disorders Institute at New York Presbyterian Hospital. His research focuses on the phenomenology of personality disorder and treatment of patients with borderline personality disorder and bipolar disorder. Past president of the Society for Psychotherapy Research, Dr. Clarkin has published numerous articles and books on psychopathology, differential treatment planning, and personality disorder.