Only two studies to date, namely the studies from Crick et al. (17) and the study from de Clercq et al. (18), have examined the stability of maladaptive personality traits in childhood. While both studies exclusively focused on borderline PD (BPD) traits among community-based, primary school-aged children, they differed regarding the instrument type and the follow-up period, as described in Table 1. While Crick et al. (17) only investigated dimensional rank-order stability, de Clercq et al. (18) investigated both, dimensional rank-order and dimensional mean-level stability. Thus, Crick et al. (17) found only moderate dimensional rank-order stability, while de Clercq et al. (18) found substantial dimensional rank-order stability over time. de Clercq et al’s (18) findings on dimensional mean-level stability indicated that children’s maladaptive trait scores generally decreased as they grow older, with a smaller decline for children who initially had higher levels of maladaptive personality traits.

Overall, ten studies reported data on the stability from adolescence to adulthood (see Table 2). Five studies were from clinical settings (21–23, 26, 27), four studies from community-based samples (19, 20, 24, 25) and one study from a high-risk sample [i.e., young adults with a history of child welfare and juvenile justice placements (10)]. From the studies conducted in clinical settings, two studies (21, 23) were conducted among patients with mixed axis I comorbidities, two studies (22, 27) were conducted among previously suicidal youth and one study (26) was conducted among depressed adolescent outpatients. Three studies (20, 22, 27) focused exclusively on BPD, while the remaining seven studies focused on any PD or most of the DSM-5 PDs. The follow-up period ranged between 6 months (27) and 10 years (10, 20) and four studies (10, 19, 21, 26) used the Structured Clinical Interview for DSM-IV Personality Disorders (SCID-II), while the remaining six studies (20, 22–25, 27) each used different measurement instruments, as presented in Table 2. Most studies focused on PD symptom counts, with only four studies (10, 19, 21, 22) investigating PD categories, three studies (10, 21, 27) reporting data on categorical rank-order stability, seven studies (10, 20, 21, 23–26) reporting data on dimensional mean-level stability, and five studies (10, 21, 24–26) reporting data on dimensional rank-order stability. Findings on diagnostic stability included two studies (21, 22) suggesting substantial stability over time and two studies (10, 19) suggesting only moderate estimates over time. Findings on categorical rank-order stability included two studies (9, 14) indicating moderate categorical rank-order stability for any PD and low to high categorical rank-order stability for individual PD diagnoses, and one study (23) suggesting low categorical rank-order stability for a BPD diagnosis. Findings on dimensional mean-level stability, however, consistently indicated significant decreases for most of PD symptoms over time (20, 21, 23–26). Only one study (10), revealed significant increases for most of PD symptoms over time. The authors concluded that this finding may be explained by the nature of the high-risk sample, as many adolescents in the child welfare and juvenile justice system have experienced severe childhood adversities (e.g., child abuse and neglect) as well as a range of other critical risk factors (i.e., unfavorable parenting practices, low socioeconomic status, childhood psychopathology, self-harming behavior, and youth delinquency) which all have been shown to be significantly associated with the stability of PDs over time. Finally, findings on dimensional rank-order stability revealed highly heterogenous patterns, with three studies (10, 25, 26) ranging from low to moderate, one study (21) ranging from low to high, and one study (24) ranging from moderate to high, depending on PD types.

Overall, 28 studies investigated the stability of PDs in adulthood (see Table 3). Most studies were from clinical settings and only four studies were from community-based samples (29, 31, 38, 42, 44, 45). One study was based on a mixed sample, including both community-based and incarcerated adults (47). Among the studies in clinical settings, seven were conducted among depressed outpatients (30, 33, 34, 37, 39, 41, 48), two were conducted among substance abuse patients (32, 52), and one was conducted among adults with long-standing eating disorders (53). The remaining studies (28, 29, 35, 36, 40, 43, 44, 46, 49, 50) included patients with mixed axis I comorbidities. In addition, nine studies focused exclusively on BPD patients (28, 31, 36, 43, 44, 46, 48, 54), one study focused on BPD and antisocial PD (i.e., ASPD) (45), one study exclusively focused on ASPD (29), and study exclusively focused depressive PD [DPD (37)]; and one study exclusively focused on narcissistic PD (i.e., NPD) (51). The remaining studies either examined “any PD” (30, 34, 39, 50, 53) or DSM-5 PDs (32, 33, 35, 38, 42, 49, 52). The follow-up period varied between 3 months (39) and 45 years (29) and most studies used the SCID-II. In contrast to studies conducted among adolescents, most studies in adulthood focused on PD categories. Thus, 19 studies (28–30, 33, 34, 36, 39–48, 50, 55) reported data on diagnostic stability, revealing highly heterogenous findings, ranging from 7.8% (44) to 80% (39). Three studies (37, 40, 50) reported data on categorical rank-order stability, with two studies (28, 39) indicating moderate and one study (43) indicating high categorical rank-order stability. Nine studies (28, 33, 40–42, 44, 49, 51, 52) reported data on dimensional mean-level stability, consistently suggesting significant declines for most of PD symptoms over time. Finally, six studies (31–33, 35, 38, 45) reported data on dimensional rank-order stability, revealing findings ranging from low to high, depending on the specific type of PD being assessed.

Although research focusing on adolescence has substantially increased over recent years, the number of studies assessing the stability of PDs in childhood and adolescence still appears to be low when compared to studies in adulthood. Part of this may be due to the widespread reluctance to diagnose PDs in adolescence because of the stigma associated with the disorder (56, 57) and the belief that personality in adolescence itself is driven by strong emotions and impulsive behavior (58, 59). Yet recent literature clearly indicates that PDs can be validly and reliably diagnosed prior to the age of 18 years (58–60) and that the stability in adolescence is comparable to that in adulthood. Nevertheless, while maladaptive personality traits can be found as early as childhood, it is reasonable to assume that more severe forms of PDs only become clinically apparent in later adolescence, when individuals have acquired skills to integrate knowledge about themselves and others into a coherent self-identity (61).

Although most studies largely differed in terms of methodological and conceptual factors, they all seem to converge in the fact that most PD categories (i.e., diagnostic stability) and PD symptoms (i.e., dimensional mean-level stability) decrease over time, while individuals’ rank-ordering (i.e., dimensional rank-order stability) seems to persist. Specifically, studies on the diagnostic stability, overall revealed that many individuals diagnosed with a PD at baseline are likely to not fulfill diagnostic criteria at follow-up. This is most notable, highlighting one of the major shortcomings of the categorical PD system for specific PDs in being based on an arbitrary diagnostic threshold that can easily be met (diagnosis PD) or unmet (no diagnosis PD) by an increase or decrease in a single criterion. This, indeed, favors diagnostic instability, while minor changes in the pathology remain unidentified and the subclinical expression of the individual’s symptoms may remain high (62). Thus, the diagnostic stability of specific PDs appears to be a rather inappropriate measure to assess the stability of PDs over time, as a categorical scaling leads to a substantial loss of information. This shortcoming could be in part compounded by looking at the stability of any PD (including PD NOS) rather than the diagnostic stability of specific PDs. As such, it may be that patients change specific categorical diagnoses but fait to discard the general diagnosis of any PD. Studies on dimensional mean-level stability mostly suggested considerable declines of PD symptoms over time. Although one might think that this is mainly due to treatment effects (63) significant decreases were also found in community-based samples, which suggests a rather natural improvement. While in healthy personality research, mean trait levels tend to change toward increasing maturity in community based settings over time [i.e., decrease in neuroticism, increase in extraversion, agreeableness, and conscientiousness (64)], this might be true for PD traits too. Indeed, the findings of Wright et al. (65), showed that decreases in avoidant PD traits were associated with increases in dominance and warmth and decreases in neuroticism. Studies on dimensional rank-order stability, however, generally indicated moderate to high stability estimates, meaning that individuals who exhibited high levels of a specific PD symptom at one time point also showed relatively high levels of that symptom at a second time point. Taken together, the mean-level of PDs and PD symptoms tends to decrease over time, regardless of participants’ age. Participants’ rank-ordering, however, tends to persist.

The extent of stability, nonetheless, considerably differed across studies, depending on the PD construct (i.e., categorical diagnoses or dimensional symptoms), the type of stability (i.e., diagnostic, mean-level or rank-order stability), and the specific PD and PD symptom being assessed. In addition, studies differed largely with respect to methodological factors, which yet again, influenced stability estimates. As such, at least six different findings must be emphasized: (a) stability estimates tend to be considerably higher when PDs are assessed dimensionally (i.e., PD symptom counts or PD traits) compared to PDs assessed categorically (PD categories). For instance, the study from Durbin and Klein (33) suggested poor to fair stability estimates for PD categories, while the stability for dimensional PD symptoms were found to be fair to moderate; (b) dimensional rank-order stability estimates seem to be higher than dimensional mean-level stability estimates, meaning that PD symptoms tend to decrease on average, while individual’s rank-ordering in a given sample remains almost the same (33, 66); (c) dimensional stability estimates appear to be higher for self-reported PD symptoms than for interview-based PD symptoms (33, 35, 38, 67). As such, Lenzenweger (38) found smaller 4 years dimensional rank-order stability estimates for interview-based PD symptoms (r = 0.61) than for self-reported symptoms (r = 0.70). Consistently, Durbin and Klein’s (33) stability estimates were 0.49 for interview-assessed symptoms and 0.69 for self-reported symptoms; (d) shorter sampling intervals will generally result in higher stability estimates compared to longer sampling intervals. For instance, dimensional mean-level changes in the Collaborative Longitudinal Personality Disorders Study [CLPS (68)]; were described as “small” at a 2 years follow-up, “medium” at a 4 years follow-up, and “large” at a 10 years follow-up interval; (e) in terms to the type of PD being assessed, cluster B PDs seem to be generally more stable than cluster A and C PDs (25); (f) PD patients in clinical settings seem to attain symptomatic remission more quickly than those from community-based samples. According to Morey and Hopwood (4), one possible reason could be that in clinical samples, participants are often drawn from treatment settings, targeting clinical remission. Therefore, participants in clinical settings tend to show faster declines (i.e., lower stability) compared to other settings. In sum, the extent of stability considerably differs according to the PD type and construct, the type of stability being assessed and several methodological factors, such as the assessment modality, sampling interval, and clinical setting.

In addition to conceptual and methodological factors, stability estimates, however, also seem to vary as a function of environmental and genetic factors. According to behavioral genetics research, individuals may be genetically predisposed to exhibit more or less stable personality traits. In other words, an individual’s overall score of PD symptoms as well as the extent to which this individual exhibits symptomatic change is strongly heritable (20). Yet individuals evolve within specific environments which may considerably affect stability estimates. As such, the study from Reichborn-Kjennerud and colleagues (45) indicated that the rank-order stability of ASPD and BPD symptoms was largely due to genetic factors, whereas symptomatic change was due to environmental risk factors. Bornovalova and colleagues (20), in contrast, found that stability and change in BPD symptoms were substantially affected by genetic factors and only modestly by environmental factors. However, the authors point out that the strong influence of genetic factors does not mean that environmental factors are unimportant, but rather indicate that the environment, indeed, is likely to influence gene expression, and emphasize the need for interventions to ensure that the individual’s family may serve as a protective factor against the manifestation of pathological traits.

Although study findings overall suggest that most PD categories and PD symptoms decrease over the lifespan, it should be kept in mind that a symptomatic remission is not necessarily accompanied by full recovery. Thus, while symptomatic remission is defined as no longer meeting diagnostic criteria for at least 2 years, full recovery is defined as attaining good social and vocational functioning in addition to symptomatic remission. In the McLean Study of Adult Development [MSAD (69)], 34.6% of BPD patients had remitted by the time of the first follow-up (2 years after the baseline assessment), about half (49.5%) had remitted by 4 years follow-up, 69% at 6 years follow-up and 93% had remitted at a 10 years follow-up (2, 54, 70). By the time of the 16 years follow-up assessment, nearly all patients (99%) had experience symptomatic remission and symptom decline stayed relatively stable, with only few patients experiencing symptomatic recurrence (55). However, notably, only half of the patients had achieved significant functional improvements over the 16 years follow-up, with some even experiencing relapse or worsened functioning. Accordingly, the authors conclude that good social and vocational functioning is more difficult to attain than symptomatic remission and, therefore, sustained recovery is much less common than sustained symptomatic remission from BPD. A decrease in PD symptoms is thus not necessarily accompanied by an increase in social and vocational functioning.

Finally, studies investigating the stability of PDs in high-risk samples are surprisingly scarce. Thus, only two studies (10, 47) examined stability estimates in high-risk samples, namely in adolescents placed in the child welfare and juvenile justice system (10) and incarcerated adults (47). This is especially striking given that individuals from high-risk samples are particularly at risk for developing a PD. Consistently, both studies (10, 47) suggested substantial increases in PD diagnoses over time (11, 45), while clinical and community-based studies overall converged in that most PD diagnoses and symptoms decrease over time.