Axis I diagnostic comorbidity and borderline personality disorder.

Borderline personality disorder (PD) has been the most studied PD. Research has examined the relationship between borderline PD and most axis I diagnostic classes such as eating disorders, mood disorders, and substance use disorders. However, there is little information regarding the relationship of borderline PD and overall comorbidity with all classes of axis I disorders assessed simultaneously. In the present study, 409 patients were evaluated with semistructured diagnostic interviews for axis I and axis II disorders. Patients with a diagnosis of borderline PD versus those who did not receive the diagnosis were assigned significantly more current axis I diagnoses (3.4 v 2.0). Borderline PD patients were twice as likely to receive a diagnosis of three or more current axis I disorders (69.5% v 31.1%) and nearly four times as likely to have a diagnosis of four or more disorders 147.5% v 13.7%). In comparison to nonborderline PD patients, borderline PD patients more frequently received a diagnosis of current major depressive disorder (MDD), bipolar I and II disorder, panic disorder with agoraphobia, social and specific phobia, posttraumatic stress disorder (PTSD), obsessive-compulsive disorder (OCD), eating disorder NOS, and any somatoform disorder. Similar results were observed for lifetime diagnoses. Overall, borderline PD patients were more likely to have multiple axis I disorders than nonborderline PD patients, and the differences between the two groups were present across mood, anxiety, substance use, eating, and somatoform disorder categories. These findings highlight the importance of performing thorough evaluations of axis I pathology in patients with borderline PD in order not to overlook syndromes that are potentially treatment-responsive.