In a population-based sample of 294 individuals with repeated personality disorder assessments spanning 12–18 years, antisocial, avoidant, borderline, histrionic, and schizotypal disorder exhibited moderate stability in individuals. Associated estimated ICCs for stability of underlying disorder over time ranged from 0.4 to 0.7–0.8. OCPD exhibited appreciable stability with estimated ICC of 0.2–0.3. Dependent, narcissistic, paranoid, and schizoid disorders were sufficiently unstable that for each, a third or more of the traits were not repeatedly endorsed by any individual in our sample.
Our primary stability findings relied on methodology that accounted for population-level shifts in trait prevalence. Such shifts were large for traits of borderline, histrionic, and schizotypal disorder; both the magnitude and direction (increase/decrease) of shift varied widely across individual traits for each of the six disorders we carried forward to formal stability analyses. This may reflect differential sensitivity of traits to aging, examiner judgments, or the presence of an axis one condition. Analyses not accounting for them yielded drastically lower estimates of stability () than did our primary analyses, which took this into account. The former assesses correlation in raw counts of traits assessed 12–18 years apart; the latter assesses the extent to which persons′ propensities to be diagnosed with traits are ranked similarly in repeated assessments whatever the accompanying shifts in trait assessment. We believe the latter target of analysis better adjudicates stability of individuals′ personalities; we suspect that population shifts primarily reflect differential assessment, not systematic changes of the trait of interest, over time. If correct, then the employment of appropriate methods for assessing personality stability merits further attention in the psychiatric literature.
Four of the ten DSM-III PDs were excluded from the primary analyses: dependent, narcissistic, paranoid, and schizoid personality disorders. For each, a considerable proportion of the pertinent traits were not endorsed at both measurement times by any participant, suggesting a combination of poor stability and sensitivity. All four personality disorders have been markedly revised in DSM IV, which this study endorses as an appropriate decision.
For a number of the other disorders (antisocial, avoidant, borderline, schizotypal), isolated traits exhibited failure of repeated endorsement over time and were eliminated from item-response analysis. These are: magical thinking, odd speech, suspiciousness, identity disturbance, feelings of emptiness, social withdrawal, irresponsible parenting, failure to plan ahead, disregard for truth, and recklessness. Their usefulness in future DSM iterations should be considered carefully.
Individual trait performance on stability
Even among traits that exhibited sufficient stability to include in formal analyses, extent of stability varied considerably, both at the population level and for individual persons. For several, the prevalence increased or decreased significantly more than on average for their disorder. Those whose prevalence decreased particularly highly were irritability/aggressiveness (antisocial disorder); social withdrawal and unwillingness to form relationships (avoidant disorder); overly reactive to minor angry outbursts and dependent (histrionic disorder); and stubbornness (OCPD). Those whose prevalence increased particularly highly over time were desire for affection (avoidant disorder); impulsivity and moodiness (borderline disorder); and excessive work devotion (OCPD). Traits whose prevalence were particularly stable over time were work inconsistency and fighting (antisocial disorder); hypersensitive to rejection (avoidant disorder); unstable relationships (borderline disorder); self-dramatizing (histrionic disorder); and emotional constriction and perfectionism (OCPD). If changes are thought to reflect differences related to measurement, then performance would be called into question for those traits whose prevalences most highly changed over time, and the particularly stable traits might be considered as “anchors” for disorders. If changes are hypothesized to occur in a given direction over time, then traits demonstrating such changes might be considered particularly sensitive to the nature of the disorder construct, and traits changing in the opposite direction would be called into question. We speculate that stable traits reflect ‘key’ elements of the PD, and traits that changed over time characterize features of PD that either are ameliorable and amenable to effects of socialization or were most influenced by the vagaries of circumstances and are less useful for PD determination.
Reasons for stability and Instability
In a review of the recent literature on PD stability Clark (2007
] points to several considerations which summarize the issues from a substantive and methodological perspective. She suggests, referencing Shea (1992)
, that PD criteria are not equal vis a vis
the construct that they measure. Some assess acute responses to circumstances based on an expectation that the trait might provoke; whereas others assess the trait per se. As expected the former have been shown to be less stable than the latter. Early or rapid change is more likely the effect of change in state rather than a change in the underlying traits. Another hypothesis put forward by Shea & Yen (2003)
is that “personality disorders are in fact stable, but the criteria currently used to define them do not adequately capture what is stable in personality disorders”. This is consonant with our findings.
She also emphasizes that PD-related dysfunction is relatively stable, more so than the diagnostic criteria. She suggests that this may give more credence to the idea of PD stability. It may be that related dysfunction is readily discernable, and therefore assessable, the limitations for the traits may be the difficulty with their measurement. Therefore functionality, attributable to personality disorder may be a more reliable measure. Though, the attribution of the manifest dysfunction to personality disorder traits/characteristics would remain a quandary.
We perceive both methodological and scientific significance in the comparison between latent variable- and GEE-based analyses. The two approaches differ philosophically. Latent-variable analysis explicitly attributes a dimensional underlying disorder “severity” to each person at each time and then estimates ICC between severities at the two assessment occasions. This approach is conceptually appealing, but to infer unseen severity from the measured trait data requires strong statistical assumptions that can affect conclusions and cannot feasibly be checked with sparsely endorsed traits. GEE analyses entail many fewer assumptions; they more simply describe the empirical data. That the latent-variable and commonality-adjusted GEE analyses yielded such similar estimates of stability heightens our confidence in both. From a scientific viewpoint, two different quantities are targeted by latent-variable analysis and raw GEE analysis, before commonality adjustment. The latter estimates stability in clinically assessed traits whereas the former estimates stability in underlying disorder severity. Disorder severity is arguably more relevant to an individual’s quality-of-life, but trait stability is what clinically assessed. To the extent that these differ greatly, improved assessment methodology is needed.
Comparison to earlier studies
There have been mixed findings from prior studies of the stability of PD stability. Those of young adults found reduced prevalence of traits and disorders over time. This concurs with normal personality studies that found substantial instability prior to the age of thirty and greater stability after that age (Costa & McCrae, 1998). Our study participants are from age eighteen across the life span.
The bulk of other studies found that PD diagnosis was not particularly stable, but was more so for dimensional measures of PD traits. We did not estimate the stability of PD diagnoses; the prevalences (reported in ) were far too rare. However, it is of note that the four disorders found to be moderately stable in the CLPS study, are among the disorders found to be stable in this study (Shea et al, 2002
). Both statistical methods in this study addressed the constellations of individual traits within the PDs; and both find evidence of stability for six PDs. This suggests that the stability is more a function of the underlying disorder construct rather than the diagnosis or the specific trait. The implication is that the broad composite of traits is a more useful measure than the specific traits themselves. Notably, analyses of trait counts suggested considerably less stability in disorder than the methods we employed for primary analyses. This discrepancy reflects data features that motivated our preference for IRT analysis, including extreme skewness of trait count distributions and shifts in trait assessment over time.
Of the original 810 CR participants, 294 participated in this study. A larger cohort would have improved the precision of the estimates. Of the large loss of participants from the original representative population cohort, a sizeable proportion had died, and was not available for follow-up. Recidivism reduced the representative nature of the sample. However, there was no evidence of a bias of selection, although this remains a possibility. Moreover, this sample is unprecedented; it is an untreated sample, examined at two points in time, 12 –18 years apart, by research psychiatrists.
The prevalence of the PDs, and their constituent traits, in the cohort were low resulting in low numbers in many of the analytic cells. Additionally, not all the DSM III PDs could be adequately studied. However, the advantages of studying an untreated sample outweigh the paucity of pathological traits, by obviating the bias inherent in studying clinical cases.
Of necessity, in a sample recruited in 1981, the older DSM III criteria were used. The performance of the PDs may have been better had the DSM IV been used. This may certainly have been the case for the four disorders not analyzed. An alternate PD structure, such as the five dimensions that we have proposed could have been studied, rather than the ten DSM disorders .