Comorbid personality disorders and the course of major depression

by Joye C. Anestis

As we've mentioned before here on PBB, drastic changes to the classification of personality disorders have been proposed for the DSM-V.  As such, personality disorders are receiving quite a bit of attention lately...and I find that very exciting!  In my own clinical work, I've seen the devastation that can be wrought by personality disorders and the often myriad of problems that accompany them.  Unfortunately, it's also been my experience that some clinicians don't always consider the presence of personality pathology when assessing Axis I disorders and, as a recent article in the American Journal of Psychiatry suggests, presence of personality disorder greatly affects the course of Axis I pathology.

The present study was headed up by Andrew Skodol, M.D. (a member of the DSM-V personality & personality disorder work group) and a number of other prominent personality researchers.  The authors  used epidemiological data (from the National Epidemiologic Survey on Alcohol and Related Disorders) to investigate the influence of all 10 DSM-IV personality disorders on the course of major depressive disorder.  I've summarized the study below (as always, check back with the original article - linked above - for more details).

Method: Data were acquired from the general population and collected in two waves. 43,093 respondents were interviewed in Wave 1 (WOW!) and 34,653 were re-interviewed 3 years later in Wave 2 (WOW again! and what a retention rate!).  Out of these folks, 2,422 of the Wave 1 responders met diagnostic criteria for Major Depressive Disorder (MDD; using a structured diagnostic interview)...and 1,996 of them participated in Wave 2 and so were included in the present study.  Because of the longitudinal nature of this study, the authors were able to conceptualize two course-related outcome variables in their analyses: 1) persistent MDD - meeting full criteria for current MDD in Wave 1 (i.e., episode within last 12 months) & full criteria for the disorder during the entire 3-year follow-up period (without the occurrence of mania), and 2) recurrent MDD - meeting full criteria for MDD in Wave 1 and again in Wave 2 (i.e., episode within last 12 months, but not the in the first 24 months immediately following the Wave 1 interview).

Results:  The author's reported a large number of analyses!  Below is a quick rundown of those findings:

• They found that borderline personality disorder had the highest percentage of persistence (28.9% [SE=2.75]) and narcissistic the lowest (14.6% [SE=2.52]).  I'm surprised by this finding in regard to narcissistic PD!  Logistic regression analyses revealed that several PDs predicted persistence, including avoidant, borderline, histrionic, paranoid, schizoid, and schizotypal.  No PDs predicted recurrence.  Among the many other variables they examined, anxiety disorders and dysthymic disorder also significantly predicted persistence.
• The authors calculated population attributable risk proportions for the effects of co-occuring psychopathology and other risk factors on persistence of MDD.  Borderline (57.3%), schizoid (47.9%), and schizotypal (45.3%) PDs, as well as any anxiety disorder (43.4%) had the highest values.  Population attributable risk proportions "indicate the proportion of persistence of MDD attributable to each disorder" (p. 262). Based on this definition, about 57% of MDD in the subjects would not have persisted into the follow-up period had they not also met criteria for borderline PD.  I admit to being a bit blown away by that!
• The authors performed a number of multivariate analyses testing the associations of PDs predicting MDD persistence:
  •   Model 1: Tested individual models for each PD, controlling for demographics.  Avoidant, borderline, histrionic, paranoid, schizoid, & schizotypal PDs were all significant predictors.
  • Model 2: Tested the same models, but added Axis I comorbidity as a control variable.  Avoidant, borderline, paranoid, schizoid, & schizotypal PDs remained significant predictors.
  • Model 3: Entered demographics, Axis I comorbidity, and all 10 PDs simultaneously, in an attempt to tease out specific PD effects. Only borderline and schizoid PDs remained significant.
  • Model 4: Family history of substance use and psychiatric illness was added to the model.  The results were virtually unchanged.
  • Model 5: Other predictors of MDD persistence (i.e., treatment history, age at first onset, the number of previous episodes, & duration of current episode in Wave 1) were added to the model.  Borderline PD remained a robust predictor of MDD persistence.

Overall, this study makes a significant contribution to the literature purporting that comorbid PDs are significant, negative prognostic indicators for MDD.  When treating clients with MDD, therefore, it is imperative that we remain aware of the possibility of comorbid personality pathology and are vigilant in treating the individual appropriately.  And borderline PD is particularly virulent!  As the new dimensional model of diagnosing PDs is being tested, I am interested to see replications of such findings.  

Joye is a doctoral candidate in clinical psychology at Florida State University and an incoming intern at the Minneapolis VAMC.