Does the diagnosis of multiple Axis II disorders have clinical significance?

A stated goal of the DSM-5 Work Group on Personality and Personality Disorders (PDs) has been to reduce the high rate of comorbidity among PDs. Few studies have examined whether the diagnosis of multiple PDs has clinical significance. In the present report from the Rhode Island Methods to Improve Diagnostic Assessment and Services project, we tested the hypothesis that patients with >1 DSM-IV PD would have more severe forms of psychopathology than patients who were diagnosed with only 1 DSM-IV PD.

A total of 2,150 psychiatric outpatients were evaluated with semi-structured diagnostic interviews for DSM-IV Axis I and Axis II disorders and measures of psychosocial morbidity.

For 8 of the 10 PDs, the majority of patients had at least 1 additional PD, although at least 20% of patients diagnosed with each PD were diagnosed with only 1 PD. Compared with patients with 1 PD, patients with ≥2 PDs had significantly more psychosocial morbidity.

The co-occurrence of PDs conveys clinically significant information. Moreover, despite high levels of comorbidity, each PD also existed as a stand-alone entity. These findings raise questions about the DSM-5 Work Group's emphasis on reducing comorbidity in Axis II.