This study assessed the overlap of BPD symptom sets and FFM traits and compared the validity of BPD features and FFM traits to predict prospective patient functioning through 10 years of follow-up. There were four overall findings. First, BPD features correlated positively with neuroticism and negatively with extraversion and agreeableness. Second, all of the BPD features and almost all of the traits significantly predicted functioning at every follow-up, although effects were strongest for BPD features, neuroticism, extraversion, and agreeableness. Third, traits tended to be more predictive of prospective and particularly longer-term (4 or more years after baseline) functioning, than BPD features. However, baseline BPD features continued to significantly relate to functioning through 10-years, and incremented traits in predicting 10-year functioning. Thus overall, the hypothesis that stable trait propensities would be more useful for longer-term predictions and less stable psychopathological symptoms would be more useful for short-term predictions was supported but only modestly so.
Fourth, certain features seemed to emerge as particularly important for different kinds of functioning. Among the FFM traits, neuroticism, agreeableness, and extraversion were significant predictors of functioning, but only the interpersonal traits extraversion and agreeableness incremented BPD features. This finding might suggest the importance of social contexts to mediate disorder-functional relations. It may also highlight the importance of adaptive or positive features that are not fully captured by diagnostic variables. For instance, the lack of severe interpersonal disruption does not necessarily portend skilled interpersonal behavior. This result therefore underscores the importance of assessing adaptive as well as maladaptive personality characteristics in the DSM-V. In contrast to these adaptive traits, the lack of incremental validity provided by neuroticism, despite its bivariate validity, may be explained by its strong overlap with maladaptive features of BPD.
This can also be seen in the validity patterns for BPD features. For instance, affective features of the disorder relate at the bivariate level to neuroticism and to functioning but the BPD affective component was not incrementally valid in regression models, suggesting that neuroticism and BPD affective features may have cancelled each other out to an extent. Among BPD symptoms, cognitive and impulse action features tended to provide the most increment over FFM traits and other BPD features. This may suggest that these are core elements of the disorder that are not fully captured by normative constructs. For instance, quasi-psychotic cognitive symptoms and impulsive actions might reflect dynamic, reactive maladaptations that are contextualized by current stressors and thus not well-captured by static, diathetic traits. However, it is also notable that these features re-emerged as significant in 10-year predictions, suggesting that BPD has a trait-like quality as well. Overall, these findings are consistent with the hypothesis that borderline traits and disorders are both overlapping and non-redundant sources of information relevant to patient functioning.
Although the use of a single PD diagnosis was an important strength of this study in that it allowed for a specific articulation of how traits may increment the features of a particular disorder, it could also be argued that including other disorders may have limited or even eliminated the effects associated with FFM traits. However, other research (Morey et al., 2007
) has shown that FFM traits increment DSM-IV personality disorders considered in combination for predicting concurrent and prospective functioning. Another potential limitation involves the prevalence of BPD in this sample and the possibility that ratings of BPD were range restricted, and that this could have attenuated BPD validity coefficients. Indeed, homogeneity of variance tests did suggest that the variance was significantly larger for those who did not meet criteria for BPD on the affect component score (S.D. = 2.73 vs. 0.90, Levene test = 167.06, p
< .001) and the interpersonal component score (S.D. = 3.50 vs. 2.83, Levene test = 4.66, p
< .05). That said, overall the standard deviations for DIB-R component scores in the full sample, as well as bivariate correlations with FFM traits and prospective functioning scores, suggest that range restriction does not fully account for study findings with regard to BPD components.
There are also limitations with respect to the measurement of traits. For instance, the FFM may have been at a predictive disadvantage because the BPD features and functioning measures were collected by interviewers, whereas the NEO-FFI is an abbreviated self-report measure. This may explain limited findings with regard to conscientiousness, which are inconsistent with other studies suggesting this trait is related to PD features (Samuel & Widiger, 2008
) and functioning (Hopwood et al., 2007
). Overall, these limitations make the validity demonstrated by the FFM in this study particularly impressive.
Overall, the current findings do not support conceptualizing traits and disorders as competitors, but rather suggest the need to integrate personality traits and disorders for clinical assessment in the DSM-V. BPD symptoms are overlapping but not completely redundant with FFM traits. Elements of both traits and BPD are important for clinical predictions of patient functioning, and disorders and traits might be differentially important depending on the kind and proximity of functioning being predicted. To the extent that some clinicians may be more comfortable using diagnostic variables than FFM traits for describing and communicating about patients (Rottman et al., 2009
; Sprock, 2003
, although see also Lowe & Widiger, 2009
and Samuel & Widiger, 2006
), these results suggest that, in addition to including ratings of FFM traits in the DSM-V, efforts should be made to train mental health professionals in how to effectively use FFM traits for patient conceptualization and clinical communication.