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Ask the Mental Health Expert Archives 2001-2004

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Cluster B Personality Disorders

Q. How often are two or more of the cluster B personality disorders diagnosed concurrently? A patient with one cluster B disorder often seems to have numerous traits of the other cluster B disorders.

A. Let's just clarify that in the DSM-IV, "Cluster B" disorders include Antisocial Personality Disorder, Borderline Personality Disorder, Histrionic Personality Disorder, and Narcissistic Personality Disorder. I refer to this as the dramatic/erratic cluster, since the pathology tends to express itself in highly emotional, impulsive, or provocative behaviors.

As your question suggests--and as DSM-IV confirms (p. 656)--one or more of these cluster B personality disorders (PDs) frequently co-occur. Cluster B PDs also co-occur with PDs from cluster A and C. A useful study of this is that of Becker et al, in the Dec. 2000 issue of the American Journal of Psychiatry. These investigators examined co-occurrence (co-morbidity) of other PDs with Borderline PD in adult and adolescent inpatients. They found that among adults with Borderline PD, 26% also met criteria for Antisocial PD; 16% for Histrionic PD; and 12% for Narcissistic PD.

Among the adolescents with Borderline PD, 10% had co-morbid Histrionic PD, while 9% had Narcissistic PD. None met criteria for Antisocial PD. In the adolescents, Borderline PD was associated with a broader range of personality pathology (outside cluster B) than in the adults. This paper will provide you with numerous additional references on the issue of PD co-morbidity.

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September 2001
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