Adolescence as a Sensitive [619567]

Adolescence as a Sensitive
Period for the Development
of Personality Disorder
Carla Sharp, PhD*, Salome Vanwoerden, MA, Kiana Wall, BA
The assessment, diagnosis, and treatment of personality disorder in adolescents
were regarded as highly controversial until very recently. Arguments against the clin-ical management of personality disorder in adolescents have included the belief
that:
1. Psychiatric nomenclature does not allow for the diagnosis of personality disorder in
adolescence.
2. Certain features of personality disorder (eg, impulsivity, affective instability, or iden-
tity disturbances) are normative and not particularly symptomatic of personality
disturbance.
3. The symptoms of personality disorder are better explained by internalizing and
externalizing disorders.
4. Adolescent personalities are still developing and therefore too unstable to warrant a
personality disorder diagnosis.
Conflicts of Interest: The authors declare that they have no conflicts of interest.
Department of Psychology, University of Houston, 126 Heyne Street, Houston, TX 77204, USA* Corresponding author.E-mail address: [anonimizat]
/C15Borderline disorder /C15Personality disorder /C15Adolescence /C15Sensitive period
KEY POINTS
/C15Adultlike personality disorder has its onset in adolescence.
/C15Rank order stability of personality disorder is moderate in adolescence and increases with
age.
/C15Personality disorder is preceded by internalizing and externalizing disorder, but not the
other way around.
/C15Personality disorder is comorbid with, but distinct from, internalizing and externalizing dis-
order throughout development.
/C15It is not until an agentic, self-determining author of the self emerges in adolescence that
personality disorder can be detected.
Psychiatr Clin N Am -(2018) -–-
https://doi.org/10.1016/j.psc.2018.07.004 psych.theclinics.com
0193-953X/18/ ă2018 Elsevier Inc. All rights reserved.

5. Because personality disorder is long lasting, treatment resistant, and unpopular to
treat, it would be stigmatizing to label an adolescent with personality disorder.1
Over the last 15 years, controversies over many of these concerns have been laid to
rest because of accumulating empirical evidence challenging these beliefs. This evi-
dence has been reviewed and evaluated in multiple recent reviews2–4and is not be
repeated here. Instead, 4 key findings have been selected from the literature onborderline disorder in adolescents for discussion, with the ultimate goal of building
an argument to support the idea that adolescence is a sensitive period for the devel-
opment of personality disorder, here defined as maladaptive self-other relatedness. Inreviewing this literature, this article focuses on borderline disorder for both pragmatic
and substantive reasons. Pragmatic, simply because enough empirical research has
been conducted on adolescent borderline personality disorder (BPD) to draw mean-ingful conclusions; and substantive, because recent evidence suggests that border-line disorder may be a proxy (or heuristic) for personality disorder in general.
5BPD
therefore serves as an appropriate paradigmatic disorder for evaluating adolescence
as sensitive period for the development of personality disorder in general.
ADULTLIKE PERSONALITY DISORDER ONSETS IN ADOLESCENCE
The first finding relevant to the argument that adolescence is a sensitive period for
developing personality disorder relates to the overwhelming evidence that personality
disorder onsets in adolescence. This finding was first shown in the Children in theCommunity (CIC
6) study, which evaluated the development and course of personality
disorder in approximately 800 youth over 20 years. Child participants were initially
assessed for personality disorders in late childhood (youngest age 9 years) and fol-lowed up thereafter during early adolescence ( m
age514 [m- mean]), midadolescence
(mage516), and early adulthood ( mage522). Because of the longitudinal nature of the
CIC study, tools chosen for the measurement of personality disorders varied over timeas needed, but followed Diagnostic and Statistical Manual of Mental Disorders (DSM)-
defined clusters and symptoms. Results of the CIC study suggest that personality dis-
order onsets in early adolescence, peaks in mid-adolescence, and subsequently de-clines into early adulthood. However, a large minority of participants (21% of the CICsample) showed an increase in personality disorder into adulthood, suggesting that
findings about the relative stability of personality disorder across the lifespan may
extend to adolescent personality disorders.
Results of other community-based studies confirm and support findings of the CIC
study. De Clerq and colleagues
7assessed the maladaptive personality traits of 477
children ( mage510.67 years) using the Dimensional Personality Symptom Item Pool
(DIPSI8), a dimensional measure of age-specific personality traits. Over a 1-year and
2-year follow-up, levels of the maladaptive personality traits disagreeableness,
emotional instability, and compulsivity declined as the children entered early adoles-cence. However, this decline was less substantial in children who showed high scores.Over the course of 4 years, in a sample of 250 subjects ( m
initialage 518.88 years),
Wright and colleagues9assessed the stability of personality disorder features in
late-adolescents and young adults. The International Personality Disorder Examina-tion (IPDE
10) assessed participants’ personality disorder criteria at each of the study’s
3 time points. The Revised Interpersonal Adjectives Scale–Big 5 (IASR-B511) was
included to measure the 3 personality factors (conscientiousness, neuroticism, andopenness) of the 5-factor model in each participant. Results indicate that the develop-
ment of adaptive personality traits such as affiliation, conscientiousness, and open-
ness, as well as a decrease in neuroticism, is associated with a decrease inSharp et al 2

personality disorder symptoms over time. In contrast, as personality disorders devel-
oped, the development of adaptive personality traits ceased or even regressed.
The summation of these findings suggests onset of personality disorder in adoles-
cents coupled with a general decline in personality disorder and an increase in adap-
tive personality traits as youth enter young adulthood. However, within these samplesthere seems to be a subset of adolescents who have diverged from the norm and
whose personality problems persist or increase into adulthood. The question then
arises whether the subset of adolescents for whom personality problems persistsmeet the threshold for a DSM-defined personality disorder.
To investigate this query, valid and reliable tools for assessing DSM criteria in BPD
had to be developed and evaluated in adolescents. Studies have shown the validityand reliability of diagnostic tools such as the Structured Clinical Interview for DSM-III-R Personality Disorders (SCID-II
12), Childhood Interview for DSM-IV Borderline Per-
sonality Disorder (CI-BPD13), the Personality Disorder Examination (PDE14), and the
McLean Screening Instrument for Borderline Personality Disorder (MSI-BPD15)
(see Ref.4for a review). Moreover, several self-report measures have also been
found to be valid and reliable, including the Minnesota Multiphasic Personality Inven-
tory – Adolescent version (MMPI-A16), Borderline Personality Questionnaire (BPQ17),
Borderline Personality Disorder Features Scale for Children (BPFSC18), Personality
Assessment Inventory Borderline subscale (PAI-BOR19), Dimensional Personality
Symptom Item Pool (DIPSI8), and the Personality Inventory for DSM-5 (PID-520). For
the BPFSC,18BPFSP,21BPFSC-11,22and PAI-BOR,19studies of sensitivity and spec-
ificity have been conducted that showed good clinical utility for these measures.
Together, these tools have been used to show that a subsample of teens meet fullcriteria for adultlike BPD in adolescents, with prevalence rates of 11% in outpatient
23
and 33%24and 43% to 49%25in inpatient samples; around 3% in UK,261% in US,27,28
and 2% in Chinese29population-based studies; and a cumulative prevalence rate of
3%,27mirroring prevalence rates in adult samples.
RANK ORDER STABILITY IS MODERATE IN ADOLESCENCE AND INCREASES WITH
AGE
The CIC study laid the groundwork for the understanding of the course and trajectory
of personality disorder in adolescence and was also the first to report stability coeffi-
cients for adolescent personality disorders in the 0.4 to 0.7 range, similar to ranges re-ported for normal personality traits in both adults and children.
6Stability coefficients
for cluster B personality disorders (borderline, narcissistic, and histrionic personality
disorders), as measured by the CIC study over the course of 9 years, were 0.63 forboys and 0.69 for girls. Analysis of the stability of BPD in adolescents, conducted
on data from the Minnesota Twin Family Study (MTFS
30), mirrored findings of the
CIC study. Bornovalova and colleagues31showed a rank order stability of 0.53 to
0.73 in the MTFS sample of adolescent female twins, assessed over a period of10 years from ages 17 to 24 years. Results from an outpatient sample in a study by
Chanen and colleagues
23show a BPD stability index of 0.54 over the course of 2 years
in a sample of 101 adolescents, aged 15 to 18 years.
Overall, as found in adult samples, it seems that adolescents’ ranking among peers
in personality disorder is moderately stable over time. Moreover, prospective studies
have shown that rank order stability of personality traits increases throughout the life-span.
32In addition, although only moderately stable, personality disorder seems to be
more stable than internalizing or externalizing mental disorders. Internalizing mental
disorder is characterized by negative emotionality, such as depressive and anxietyAdolescence and Personality Disorder 3

symptoms. Externalizing disorder encompasses disruptive or impulsive behavioral
symptoms, such as delinquent or dangerous behaviors. For example, the CIC study6
found that the stability of internalizing and externalizing symptoms was consistently
lower than the consistency of cluster B personality disorder symptoms. This finding
suggests that, during adolescence, borderline disorder and other cluster B symptomscan be expected to be more enduring and long lasting than periods of internalizing and
externalizing symptoms. De Clerq and colleagues
7found that, across 3 years and 3
time points, externalizing symptoms, as measured by the Dutch version of the ChildBehavior Checklist (CBCL
33,34), showed steeper and continued decline beyond those
of maladaptive personality traits. These data point to normative developmental matu-
ration processes wherein children grow out of externalizing behaviors, whereas mal-adaptive personality may be more persistent or may have functional impairmentthat persists beyond the normative decline of DSM-based symptoms.
35,36
PERSONALITY DISORDER IS PRECEDED BY INTERNALIZING AND EXTERNALIZING
DISORDER BUT NOT THE OTHER WAY AROUND
Stepp and colleagues37systematically reviewed the antecedents of BPD, identifying
39 studies that considered risk factors for BPD. Nineteen of these studies examinedinternalizing and externalizing mental disorders as a predictor of BPD, and 16 reported
either internalizing or externalizing disorder as a significant predictor. For instance,
Belsky and colleagues
38found that borderline personality traits, measured in adoles-
cents at age 12 years, were more common in those who had shown more behavioral
and emotional problems at the age of 5 years. Stepp and colleagues39also showed
that both internalizing (depression and suicidality) and externalizing (substance usedisorder) mental disorder are associated with later BPD symptoms in adolescence.
Based on findings of additive and interactive effects of internalizing and externalizing
symptoms on borderline disorder over time, Bornovalova and colleagues
40suggested
that BPD traits measured in adulthood may be best understood as preceded by an
inherited vulnerability for internalizing and externalizing disorders.
Internalizing symptoms have also been independently shown to predict later BPD.
Krabbendam and colleagues41found that posttraumatic stress, depressive symp-
toms, and dissociation increased the risk for BPD in adulthood among detained,
adolescent girls. In addition, internalizing constructs such as experiential avoidance
have been shown to be predictive of borderline features in adolescents.42Similarly,
externalizing symptoms, particularly attention-deficit/hyperactivity disorder (ADHD)
and oppositional defiant disorder (ODD), have also been independently shown to pre-
dict BPD. An early study of the antecedents of personality disorder by Rey and col-leagues
43showed that young adults who had been diagnosed with a disruptive/
externalizing disorder in adolescence showed higher rates of personality disorders
than those diagnosed with emotional/internalizing disorders, at rates of 40% and12% respectively. In a clinical sample of male patients, initially aged 7 to 12 years,Burke and Stepp
44found that ADHD and ODD significantly predicted BPD symptoms
at age 24 years, even when accounting for substance abuse, other personality disor-
ders, and physical punishment. Complementing this finding, in a large sample of girlsaged 8 to 13 years from the Pittsburgh Girls Study, Stepp and colleagues
45also iden-
tified ADHD and ODD as unique predictors of BPD symptoms at age 14 years.
Results of the aforementioned studies cumulatively suggest that both internalizing
and externalizing disorders in childhood and adolescence are significant predictors
of BPD, or an increase in BPD symptoms, in adolescence and adulthood. In contrast,
borderline features seem not to precede internalizing and externalizing disorders. ForSharp et al 4

instance, Lazarus and colleagues46and Bornovalova and colleagues40both showed,
in samples of adolescents aged 14 to 17 and 14 to 18 years respectively, that, afteraccounting for cross-sectional relations and temporal stability between substance
use problems and borderline features, the latter were not a causal antecedent to
the former. More specifically, although BPD symptoms were associated with contem-poraneous increases in alcohol use, the lagged and sustained effects of BPD on
alcohol use were not significant, whereas the reverse was significant.
40,46However,
it is notable that most studies that examined longitudinal associations between BPDand internalizing and externalizing disorders either did not measure BPD symptoms
before adolescence or did not explicitly test the hypothesis that BPD precedes inter-
nalizing and externalizing disorders, which is an important area for future research. Asdiscussed later, based on developmental considerations, the authors think it unlikelythat personality disorder (defined as maladaptive self-other relatedness) would pre-
cede internalizing and externalizing disorders even if it were measured.
PERSONALITY DISORDER IS COMORBID WITH, BUT DISTINCT FROM,
INTERNALIZING AND EXTERNALIZING DISORDERS THROUGHOUT DEVELOPMENT
In addition to being antecedents of BPD in adolescents, internalizing and externalizing
mental disorders are highly comorbid with BPD throughout adolescence and into
adulthood. Similar to adult samples, comorbidities in adolescents with BPD range
from 50% in a community sample6to 86% in a clinical sample.47,48For example, in
a sample of 177 adolescent outpatients, Chanen and colleagues49found that subjects
with BPD showed the highest levels of psychiatric severity and comorbidity, followed
by adolescents with no BPD but another personality disorder, and finally adolescentswith no personality disorder. Similarly, Ha and colleagues
24found that inpatient ado-
lescents with BPD had higher rates of comorbidity than their psychiatric control peers
for mood disorders (70.6% vs 39.2%), anxiety disorders (67.3% vs 45.5%), and exter-nalizing disorders (60.2% vs 34.4%). In addition, adolescents with BPD scored higher
on the Youth Self-Report (YSR
50), a dimensional measure of internalizing and external-
izing mental disorder, than controls. In addition, Sharp and colleagues51report that
adolescents with BPD showed significantly higher rates of complex comorbidity, asdefined by Zanarini and colleagues,
52wherein individuals must have any mood or anx-
iety disorder plus a disorder of impulsivity (ie, BPD).
Although evidence for comorbidity between internalizing, externalizing, and person-
ality disorders is unequivocal, there is also strong evidence that BPD is not fully sub-
sumed by internalizing and externalizing mental disorders. James and Taylor53as well
as Eaton and colleagues54factor analyzed internalizing, externalizing, and borderline
disorders (at the level of diagnosis) and showed that although BPD was a confluence
of both internalizing and externalizing disorders (ie, loaded onto both internalizing and
externalizing latent factors), there was enough variance not captured by these latentfactors to suggest that BPD cannot be fully explained by these disorders. These find-ings were replicated in a study by Sharp
51in adolescence.
That borderline disorder seems to denote unique disorder beyond internalizing and
externalizing disorders despite high rates of comorbidity is further supported by lon-gitudinal studies in adolescents. For example, Wright and colleagues
35used data
from the Pittsburgh Girls Study to further elucidate the understanding of within-
person change, as well as outcomes, associated with adolescent BPD. Latent growthtrajectories, based on 2450 adolescent girls aged 14 to 17 years, revealed that BPD
symptoms were at least moderately associated with every aspect of psychosocial
functioning measured, but, when internalizing and externalizing disorders wereAdolescence and Personality Disorder 5

controlled for, BPD was related to poorer outcomes in social skills, self-perception,
and sexual activity. Other functional domains that did not remain significant outcomesfor borderline disorder once internalizing and externalizing disorders were controlled
for include academic performance, extracurricular activities, and global functioning.
That functional impairment in the interpersonal domain seems to be uniquely andmore persistently associated with borderline disorder beyond that of general relations
to internalizing and externalizing disorders is an important finding and begins to point
to the possibility that personality disorder is particularly important for understandingand predicting functional outcomes in the interpersonal domain. Moreover, borderline
disorder may be particularly important for predicting severity of mental disorder, as
shown in a sample of 177 adolescent outpatients in whom BPD significantly predictedgeneral mental disorder as measured by the YSR
50and the Young Adult Self-Report
(YASR55) peer relationships, self-care, and family and relationship functioning, beyond
other personality disorders or axis I disorders.49Similarly, Sharp and colleagues56
found that BPD provided incremental predictive value for both suicidal ideation and
deliberate self-harm, relative to major depressive disorder, in a sample of 156 adoles-
cent inpatients.
In summary, borderline disorder is comorbid with, but not fully explained by, inter-
nalizing and externalizing mental disorders across the lifespan.54Internalizing and
externalizing disorders seem to be developmental antecedents of BPD37and the
risk factors for borderline disorder are also nonspecific to the disorder and sharedwith internalizing and externalizing disorders.
37The risk profile for borderline disorder
is almost identical to that of various other internalizing57–59and externalizing disor-
ders.60,61These conclusions may suggest that, in the developmental path to border-
line disorder, internalizing and externalizing disorders are a stepping stone, asindicated by their antecedence to, comorbidity with, and shared risk factors for
borderline disorder.
ADOLESCENCE AS A SENSITIVE PERIOD
The evidence presented thus far naturally raises the question of whether adolescence
poses a sensitive period for the development of personality disorder. As discussedearlier, personality disorder onsets in adolescents and although some adolescents
adhere to the normative decline in personality disorder through early adulthood, a sub-
set of adolescents’ symptoms increase or stagnate. This article has discussed howthis subset likely meets clinical threshold for adultlike personality disorder categori-
cally defined. It has also shown that personality disorder after onset in adolescence
remains moderately stable, and more stable than internalizing and externalizing disor-ders, which are antecedents (but not consequences) of personality disorder. In addi-
tion, although internalizing and externalizing disorders are comorbid with personality
disorder, personality disorder seems to uniquely associate with dysfunction (specif-ically in the domains on interpersonal function) and psychiatric severity. It thereforeseems that something special happens in adolescence that allows internal and
external mental disorders to ripen into personality disorder given the right circum-
stances. This article argues that adolescence represents a unique developmentalperiod for the onset of personality disorder if internalizing and externalizing disorders
are left untreated and in the context of biological vulnerability and stressful life events,
because it is during adolescence that an agentic, self-determining author of the selfemerges.
62
It has long been noted that a key developmental task of adolescence is the emer-
gence of a mature sense of self or identity, which can be identified by intrapersonalSharp et al 6

and interpersonal continuity along with the presence of an autonomous self.63Howev-
er, to understand the process of self-maturation that consolidates during adolescenceand how this leads to a sensitive period in the development of personality disorder, it is
important to consider the typical trajectory of self and identity development. Harter
64
described the self as both a cognitive and social construction. As cognitive skills
continuously emerge and mature through early adulthood, the organization and struc-
ture of the self are constrained by which developmental tasks an individual has
achieved. Similarly, social interactions, which change form across development,have an influence on the content and valence of individuals’ self-representations.
Although the term identity is often used synonymously with self-related constructs
such as self-representations or self-concept,
65investigators have conceptualized
identity to be the way an individual makes sense or meaning from their self-con-cepts.
66Thus, identity is often studied with autobiographical narratives in which peo-
ple are evaluated in their ability to integrate their autobiographical past and imagined
future in a coherent way.67Although impairments in various aspects of the self may
emerge, depending on the stage of development, it is proposed that it is a disruption
in identity that characterizes the core of personality disorder.68The typical develop-
mental trajectories of self-processes are described here, as well as how it is not untiladolescence that an integrated and coherent identity is able to emerge.
Self-development emerges in infancy with basic functions; infants show body
awareness by physical self-recognition,
69and an early sense of agency is apparent
with children as young as 6 months old carrying out and understanding others’
goal-directed behavior.70In the second year of life, children start to show the use of
personal pronouns (eg, saying “me”71). Very young children are able to label charac-
teristics of themselves, suggesting a metarepresentation of the self, or the idea of“me.”
72Also beginning in early childhood, understanding of intent (both for the self
and other) and theory of mind (mentalizing) is apparent, with children able to describe
emotional experiences of the self and other as well as imitating and following behav-ioral intent of others.
73Self-awareness is further apparent after age 3 years, with chil-
dren developing the capacity for autobiographical memory and narratives, which,
although largely facilitated by caregivers, represent a base by which children cometo understand themselves within the greater social context.
74These normative
achievements may be disrupted by maladaptive caregiving experiences, such as
abuse or neglect, which can further impair the ongoing development of the self at laterages.
75However, because of cognitive limitations, self-representations remain largely
positive, often unrealistically, and social comparison for the purpose of self-evaluation
is not present, which also serves a protective function for the early self.64These devel-
opmental processes also play out similarly in the brain. Developmental neuroimagingstudies have found that the dorsal medial prefrontal cortex (MPFC), which supports
self-reflection, is one of the brain regions that develops last and comes on line in
adolescence.
76Until the MPFC matures in adolescence, social evaluation is not inter-
preted in any self-referential way and is unlikely to lead to self-conscious emotions and
autonomic arousal.77Similarly, cognitive constraints on mentalizing ability in early
childhood are associated with reduced awareness of others’ appraisals of the selfand social comparison is not used to build the concept of self.
78
Through childhood these early emerging self-processes continue to develop with
the support of increased perspective-taking skills and greater sense of self-agency.64
As children increase in their self-understanding through middle childhood, they morespontaneously and thoughtfully begin to use this information for social comparison
and self-evaluation.
79Further, children internalize information regarding cultural
values, which guide choices and interests with regard to roles, institutions, and valuesAdolescence and Personality Disorder 7

as well as informing self-evaluation.80By late childhood, self-evaluation has become
more realistic, leading to a decrease in the egocentrism characteristic of early child-hood and a parallel decrease in self-esteem, which can be expressed verbally.
81
This decrease in egocentrism occurs because the perspectives of others are startingto be internalized and self-evaluations are based on the standards of others.
82
Increased cognitive skills lead to children’s autobiographical memories showing con-
tinuity and greater complexity as both positive and negative attributes begin to be in-
tegrated.64Also, as children move through the school system, social comparison
becomes more salient and frequent.83
By early adolescence, these changes reach a peak with expanded cognitive skills,
including self-consciousness and concern about the appraisal of others.84Social
awareness has increased dramatically, particularly with regard to others’ perspectivesabout the adolescent. This increase is caused by more mature perspective-taking
abilities that are developing in the context of adolescents forming more intimate rela-
tionships with peers. The joint result of these 2 developments is shared reflection withpeers such that the individual’s personal goals become integrated the goals of close
others.
64Further, adolescents develop an imaginary audience, referring to the percep-
tion that others are as preoccupied with their behavior as the adolescents are, which ishypothesized to be a result of increased perspective taking and social awareness.
85It
has been suggested that the imaginary audience phenomenon is a function of the
separation-individuation process of adolescence such that constructing an imaginaryaudience creates a sense of closeness and importance among peers as adolescents
renegotiate relationships with parents, which is a reflection of the expansion of
intimacy and close relationships beyond the family system into peers and potentialromantic partners.
86
Selman87described the ability acquired during early adolescence of stepping
outside the social dyad to view the self as a social object that is observed by others.
With this ability, young adolescents move to introspection to try to determine whichperspectives to internalize as defining features of their identity. This process has the
potential of leading to doubt and uncertainty as adolescents consider multiple per-
spectives and opinions.
88,89In addition, because expanded cognitive skills mean
that adolescents are able to form more abstract representations of themselves, there
is a liability that self-representations become more removed from concrete behavioral
evidence and therefore may be inaccurate.90In addition, although preadolescents’
unreflective self-acceptance buffers them from potential negative self-image,91
adolescence is a time when individuals become able and begin to examine multiple
self-hypotheses that not only may be negative but also may be overwhelming based
on the numerous context-dependent or relationship-dependent roles.90In addition,
although the tendency to compartmentalize different selves from other contexts dur-
ing preadolescence acted as a buffer against negative outcomes by reducing the pos-
sibility that negative attributes in one sphere may generalize to others, this is no longerthe case. Another developmental advance is the ability to directly compare and
contrast these different self-images that often seem contradictory to one another.
92
It is not until late adolescence that adolescents are able to integrate these various
self-representations to resolve apparent contradictions; this means that adolescence
is largely characterized by intrapersonal conflict, confusion, distress, and potential
instability in self-representation.93
In addition to cognitive advancements that open the door for potential disruptions in
self-development, environmental changes during this phase of life represent addi-
tional strain. Not only is high school generally a new social environment but teachers
and parents hold more stringent expectations for adolescents. These environmentalSharp et al 8

changes set the stage for new dimensions of social comparison (eg, academics, extra-
curricular activities, appearance), with the environment placing greater emphasis onsocial comparison (eg, posting grades or accomplishments publicly at schools
80). In
addition, consequences of academic achievement gain greater weight with adoles-
cents starting to consider possible future selves, such as college and potential occu-pations. Considering both cognitive and environmental changes that take place during
adolescence, it is not surprising that individual differences in self-esteem are much
more apparent during this age,
81largely dependent on perceived adequacies in
certain domains as well as perceptions of approval from others.
Despite the increased cognitive skills developed during adolescence, there re-
mains an underdeveloped prefrontal control over these new capacities. Therefore,extreme or ineffectively applied use of these new cognitive capacities may beobserved.
64However, by late adolescence, the ability for causal coherence is devel-
oped, which allows adolescents to develop narratives that explain how chronologic
events in their life are linked.94In addition, by midadolescence to late adolescence,
individuals are able to identify overarching themes, values, or principles that integrate
different events in their lives, called thematic coherence.94Both causal and thematic
coherence are caused by the adolescent’s newly acquired ability for higher-orderabstractions, which is used to meaningfully integrate previous seeming con-
tradictions in self-representations, allowing identity to consolidate. In addition, by
late adolescence, individuals start to normalize potential contradictions in self-representations, which serves to reduce internal conflict.
93As adolescents move
into young adulthood, they gain a greater sense of agency as they take steps to
become their future selves. Although the described developmental tasks are largelya result of cognitive development through adolescence, it is also suggested thathigher level acquisitions require greater social scaffolding. Therefore, others assist
adolescents in fostering new skills in order to integrate contradictory self-images
and normalize potential contradictions.
95,96
The monumental achievement of developing an agentic, self-determining author of
the self during adolescence is offset by the significant vulnerability associated with
failure of achieving such integration, consolidation, and coherence. It is only in thecontext of the normative emergence of the agentic self that disturbed self-other func-
tion can develop and be observed and diagnosed. The authors suggest that adoles-
cence poses for the first time a developmental opportunity for DSM-5 section IIIcriterion A (impaired function in self-other relatedness) to emerge as a qualitativelydifferent level of mental disorder beyond internalizing and externalizing disorders,
and on the severity pathway toward psychotic disorders.
97As described elsewhere,97
correlated but distinct internalizing and externalizing problems begin to emerge in pre-
adolescence in the form of anxiety and depressive symptoms predominantly in girls,
and ADHD and conduct problems predominantly in boys. If these disorders are left un-
treated, and in the context of predisposing biological vulnerabilities and interactingstressful life events, internalizing and externalizing problems form a platform for the
development of personality disorder during adolescence, characterized by a qualita-
tively different levels of mental disorder in the form of maladaptive self-other related-ness; qualitatively different because this new level of mental disorder cannot be
adequately captured by dispositional traits associated with internalizing and external-
izing problems (ie, temperamental traits are insufficient to describe personality disor-der because they constitute merely one component of the personality system).
98
Personality, and therefore personality disorder, is integrated and organized in nature99
and the task of organizing traits into a coherent whole becomes a major focus ofadolescence. Just as the Big Five can readily be observed in preadolescent children,Adolescence and Personality Disorder 9

so can maladaptive dispositional traits (DSM-5 section III, criterion B; eg, neuroticism,
antagonism, disagreeableness, and psychoticism), which can be readily evaluated byassessing internalizing and externalizing mental disorders.
100With the emergence of
an agentic, self-determining actor, self-narrative becomes a vehicle by which traits
are made sense of in the context of past, current, and future events. Although this pro-cess of identity formation proceeds smoothly for most adolescents, for some this pro-
cess is characterized by incoherence, inconsistency, confusion, and distress,
ultimately resulting in a personality structure resembling DSM-5 section III criterionA personality function. The progression from internalizing/externalizing to a next level
of mental disorder characterized by maladaptive self-other function brings with it in-
creases in psychiatric severity (p factor
101), more persistence and stability, and lower
population-based prevalence rates of disorder.97Kernberg’s102model shares fea-
tures with the proposed developmental model in that borderline disorder is identified
as having heuristic value in representing what is common to all personality disorders
(criterion A) and it lies on the severity pathway between internalizing/externalizing andpsychotic mental disorders. This article reinterprets Kernberg’s
102original model in
the light of developmental mental disorder data from the last decade and proposes
that criterion A (personality disorder beyond maladaptive traits) cannot be diagnosedin any meaningful way until children reach adolescence to begin the task of integrating
disparate representations into a coherent whole in the service of identity formation.
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