Joel F. McClough
John F. Clarkin
The prevalence of personality disorders in the general population is approximately 10%-15% (Maier, Lichtermann, Klinger, & Heun, 1992). In clinical settings, the prevalence increases substantially (see Matia & Zimmerman  for review). Personality disorders tend to co-occur with other more acute symptom-based (i.e. Axis I) disorders with great frequency (Maier, Minges, Lichtermann, & Heun, 1995). The Axis I disorders commonly associated with, and negatively affected by, comorbid personality disorders include (but are not limited to): major depression (Gunderson & Phillips, 1991; Shea, Widiger, & Klein, 1992), anxiety (Stein, Hollander, & Skodol, 1993), social phobia (Hirschfeld, Shea, & Weise, 1991), eating disorders (Godt, 2002), and schizophrenia (Hogg, Jackson, Rudd, et al. 1990). This substantial comorbidity is important, because the presence of a personality disorder often complicates proper diagnosis, interferes with effective treatment, and negatively contributes to the clinical course of many Axis I disorders (McGlashan, Grillo, Skodol et al., 2000).
Because of increasing concern over the cost, availability, and efficiency of mental health services in the United States, several large epidemiological studies have been conducted to assess treatment utilization by mental health consumers. Research has shown that personality disorder clients,