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Research Article                                                                                                                                        Open Access

## The Relationship between Personality Disorders and Quality of Life in Adolescent Outpatients

Hans Ole Korsgaard 1.2 , Svenn Torgersen 3,4 , Tore Wentzel-Larsen 3,5 , Randi Ulberg 2,6

1 Department for Child and Adolescent Mental Health (The Nic Waal Institute), Lovisenberg Diakonale Hospital, Oslo, Norway; 2 Institute of Clinical Medicine, University of Oslo, Norway; 3 Centre for Child and Adolescent Mental Health, Eastern and Southern Norway, Oslo, Norway; 4 Department of Psychology, University of Oslo, Norway; 5 Norwegian Centre for Violence and Traumatic Stress Studies, Oslo, Norway; 6 Vestfold Hospital Trust, Norway;

*Corresponding author: hansole.korsgaard@lds.no

## Abstract

Background: During recent years, there has been an increasing focus on the benefits of the early detection and treatment of personality disorders in adolescents. Previous studies of adults have shown that the number of personality disorder criteria met is negatively correlated with a patient's quality of life and general functioning.

Objective: The aim of the present study was to investigate the prevalence of personality disorders, particularly with regard to the correlation between the number of personality disorder criteria fulfilled and self-perceived quality of life. Distribution according to gender and age in a clinical sample of adolescent outpatients were also considered.

Method: This study included 153 adolescents between the ages of 14 and 17 years who were referred to a mental health outpatient clinic. Personality disorders were assessed using the Structured Interview for DSM-IV Personality. Quality of life was assessed using the Youth Quality of Life Instrument - Research Version, which is a 41-item questionnaire that covers broad aspects of quality of life. Axis I disorders were assessed using the Mini International Neuropsychiatric Interview.

Results: Results demonstrated that 21.6% of the adolescents met the diagnostic criteria for at least one personality disorder. A relationship between the number of personality disorder criteria met and reduced quality of life was found. No significant gender differences  with  regard to  the  prevalence of each of  the  personality disorders  were  revealed. Adjustment for  the presence of Axis I disorders did not appreciably affect these findings

Conclusion: The present study indicates that reduced quality of life as a result of the number of personality disorder criteria met affects adolescents in much the same way that it does adults. This further emphasizes the clinical importance of including quality of life assessment as part of the general diagnostic procedures used with adolescents.

Keywords: Personality disorder; quality of life; adolescent; outpatient

## Introduction

Personality Disorders in Adolescents

Personality disorders are defined as relatively enduring and maladaptive patterns  of  experiencing life, coping with problems, and relating to others. In the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), personality disorder categories may be applied to adolescents when the individual's  particular  maladaptive  personality traits appear to be pervasive, persistent, and unlikely to be limited to a particular developmental state or to an episode  of  an  Axis  I  disorder.  With  the  formal exception  of  antisocial  personality  disorder,  it  is possible  to  diagnose  any  personality  disorder  in  a person who is less than 18 years old if the diagnostic features have been present for at least one year (1). This information remains unchanged in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (2).

The prevalence of personality disorders in adults has been studied in the general population (3) as well as in different clinical samples (4). Personality disorders are common conditions, with prevalence of about 13% in the general adult population, up to 40% in  adult  outpatient  samples,  and  up  to  71%  in inpatient samples when using semi-structured diagnostic interviews (5). In adolescents, prevalences range from 6% to 17% in community samples and from 41% to 64% in clinical samples (6).

Research supports the assumption that pathological personality traits emerge at an early age and are related to health-risk behaviors (e.g., failing to complete  secondary  school,  alcohol  dependence, getting  in  trouble  with  police  and  violent  crime, unsafe sex, dangerous driving habits) during adolescence  and  young  adulthood  (7,8).  This  has been  demonstrated  by  longitudinal  cohort  studies like  the  Dunedin  study,  in  which  early  appearing temperamental  differences  were  shown  to  have  a pervasive influence on life-course development and to correlate with personality structure, interpersonal relations, psychopathology, and crime in adulthood (7-9).

There has been increased interest in the concept and delineation of personality disorders during childhood  and  adolescence  (10).  Earlier  findings support  the  view  that  personality  disorders  can  be traced  back  to  adolescent  emotional  problems  and disruptive behavior disorders (11). Caspi and colleagues have shown that behavior observed in 3year-old children can be clearly linked to psychiatric problems during early adulthood (12). Furthermore, the long-term study of the same population demonstrated strong links between behavioral qualities observed at the age of 3 years and personality functioning measured at the ages of 18 and 26 years (8).

Personality disorders may have a better prognosis than  originally  assumed  (13).  However,  findings indicate that maladaptive personality trait constellations are more stable in their structure than personality  disorder  diagnoses  per  se.  Maladaptive personality traits may change in severity or expression over time, but they often lead to persistent functional impairment and reduced quality of  life,  even  though  the  diagnostic  threshold  for  a personality disorder is no longer reached (14,15).

An important focus is on the matter of precursors and possible pathways: in other words, the interplay of temperament and personality (16). This research is limited in part by the fact that the current diagnostic systems  do  not  readily  facilitate  the  recognition  of personality  pathology  before  the  age  of  18  years. Many clinicians are reluctant to diagnose personality disorders during adolescence; they may view pediatric personality deviations as reflective of given developmental stages, despite evidence that certain adolescents  are  indeed  at risk for the  eventual development  of  personality disorders as adults.

Studies  have  shown  that  the  late  identification  of these disorders prevents timely treatment and potentially increases morbidity (17-19).

A  further  complicating  factor  may  be  that  the childhood symptoms of personality disorders are not necessarily  identical  to  the  symptoms  of  the  same disorders as they manifest in adults (20). One study compared the prevalence rates of DSM-IV borderline  personality  disorder  in  English  11-yearolds and American adults. The results suggested that late-latency children are about half as likely as adults to meet DSM-IV criteria for borderline personality disorder and that gender does not play a defining role in symptom  expression  (21). Few  studies have reported  about  gender  differences  in  personality disorders in adolescents (6).

## Personality Disorders and Quality of Life

Quality of life is a concept of considerable societal importance  (22).  A  study  from  the  Netherlands investigated the burden of disease in a large sample of  patients  with  personality  disorders.  The  results showed that the total number of personality disorder diagnoses-rather than the specific type-was related to quality of life. In this study, patients with personality disorders experienced a high burden of disease that was comparable to that experienced by patients with severe somatic illnesses like rheumatic disease,  lung  cancer,  or  Parkinson's  disease  (23). Findings from the general adult population indicate that personality disorders are important predictors of quality of life, even more so than sociodemographic variables, somatic health, and Axis I disorders (24,25).

Studies of adults have found a linear relationship between the number of personality disorder criteria met and the actual impairment of quality of life (26). Personality  disorders  during  adolescence  seem  to have  a  negative  impact  on  quality  of  life  in  young adults.  A  combination  of  Axis  I  disorders  and personality disorders during adolescence may lead to an even poorer quality of life (27-29).

## Aims

The  objectives  of  the  present  study,  which  was performed on a clinical sample of adolescent outpatients, was to do the following:

1. Investigate the prevalence of personality disorders, including possible gender differences.
2. Investigate the relationship between the number of personality  disorder  criteria  met and the patient's self-perceived quality of life. We  also  wanted  to  assess  age  and  gender differences to determine whether adjustment for Axis I disorders affected the relationship between personality disorders and quality of

life;  and  to  discover  whether  there  were interactions between the number of personality disorder criteria and the patient's age and gender.

## Materials and Methods

## Ethics

This study was approved by the Regional Committee for  Medical  Research  Ethics  for  Eastern  Norway (REK: 11395) and by the Norwegian Data Inspectorate. Informed written consent was obtained from all patients. Consent was also obtained from the parents of patients who were less than 16 years old.

## Participants

The  sample  consisted  of  adolescents  between  the ages of 14 and 17 years who had been referred to a mental  health  outpatient  clinic  for  children  and adolescents in Oslo (The Nic Waal Institute, Lovisenberg  Diakonale  Hospital).  The  Nic  Waal Institute  is  one  of  the  largest  clinics  of  its  kind  in Norway;  it  serves  four  city  districts  and  a  total population of 25,000 children and adolescents from 0 to 17 years old. The Institute serves a population of  mixed  socioeconomic  status  comprised  of  all social classes, including immigrant workers and welleducated middle-class and upper-class families.

Study enrollment took place from February 2005 to April 2007. All referred patients in the study's age group  were  asked  to  participate.  Exclusion  criteria were the need for immediate hospitalization or other urgent therapeutic measures, clinically assessed mental retardation, a lack of fluency in the Norwegian language, and the absence of the evaluator at the time of referral.

## Measures

Axis  I  disorders. The  Norwegian  translation  of  the Mini International Neuropsychiatric Interview (MINI)  version  5.0.0  was  used  to  assess  Axis  I disorders (30,31).

Personality  disorders. The  Norwegian  version  of  the Structured  Interview  for  DSM-IV  (SIDP-IV)  (32) was used to assess personality disorders. The SIDPIV  is  a  comprehensive  semi-structured  diagnostic interview for DSM-IV personality disorder (Axis II) diagnoses. The SIDP-IV has been used in numerous studies  in  different  countries,  including  Norway (3,11,33). It covers 14 DSM-IV Axis II diagnoses as well as conduct disorder as a separate Axis I disorder. The  Axis  II  diagnoses  comprise  the  10  standard DSM-IV  personality  disorders  (paranoid,  schizoid, schizotypal, borderline, histrionic, narcissistic, antisocial, obsessive-compulsive, dependent, and avoidant), the three provisional DSM-IV personality disorders  (self-defeating,  depressive,  and  negativistic), and mixed personality disorder.

All questions on the SIDP-IV address the typical or  habitual  behavior  of  the  subjects  during  the previous five years. Each diagnostic criterion is rated on a four-point scale: 0 = criterion not present; 1 = subthreshold level of the trait present; 2 = criterion being present for most of the last five years; and 3 = criterion strongly present. Scores of 2 and 3 indicate the presence of a criterion according to the DSM-IV (32).

In accordance with the diagnostic practice applied in  other  studies  of  personality  disorders  during adolescence, the DSM-IV age criterion for antisocial personality disorder was waived (34). As a result of the  participants'  ages,  we  also  waived  the  5-year symptom  duration  criterion,  instead  opting  to  use two years of symptom duration as a criterion. This is in  accordance  with  the  criterion  used  in  previous studies that assessed adolescent personality pathology (6,34).

Quality of life. A Norwegian translation of the Youth Quality of  Life  Instrument -  Research  Version (YQOL-R) was used to assess of quality of life. The YQOL-R  is  a  self-scored  questionnaire  that  was developed with the goal of focusing on the positive aspects of adolescence (35). It covers broad aspects of  quality  of  life,  with  a  total  of  41  items  in  four topical  domains:  self,  relationships,  environment, and general quality of life. Its psychometric properties are satisfactory (36), and it has been used in various clinical and non-clinical settings (37,38).

The  adolescents  rated  the  YQOL-R  items  on  a scale that ranged from 0 (most severe) to 10 (best). The primary outcome with regard to quality of life was the general quality of life domain of the YQOLR. In the present study, Cronbach's alpha was found to be 0.94.

## Procedures and Assessment

One  evaluator-the  first  author-was  assigned  to the  study  and  assessed  all  of  the  participants.  All patients referred to the clinic while the evaluator was present were asked to participate in the study. After written consent was obtained from the patients, the diagnostic  interviews  were  performed  at  the  Nic Waal  Institute  as  an  initial  psychiatric  assessment. The  evaluator,  a  male  physician  with  21  years  of clinical experience, was a specialist in both psychiatry and child and adolescent psychiatry. He was trained in evaluation with the SIDP-IV by the second author, an  experienced rater  who  had  previously  evaluated patients and reported for comparable studies (3,39). Twenty ratings  were  discussed  and  found  to  be  in accordance  with  the  ratings  of  the  experienced evaluator.  Axis  I  conditions  were  assessed  by  the same  evaluator,  who  had  also  been  trained  by  the translator of the Norwegian version of the MINI.

After the completion of the initial assessment, the patients were assigned to further clinical evaluation and treatment by clinicians other than the evaluator in the outpatient clinic.

## Statistical Analysis

Descriptive statistics were calculated for the relevant mental  health  status  variables  and  expressed  as means (standard  deviation)  and  frequencies  (%)  as appropriate. Prevalence of personality disorders with 95% Blaker's confidence intervals were estimated for the total sample and for each gender separately, with testing for gender differences and comparison with the  general  adult  population  via  exact  chi-squared tests (40).  The  non-linearity  of  the  relationship between  the  total  number  of  personality  disorder criteria  met  and  the  quality of life  was investigated graphically with separate locally weighted smoothing (LOWESS)  curves  for  each  gender.  Within  each disorder, this relationship was also explored graphically. The relationship of self-perceived quality of  life  with  the  number  of  personality  disorder criteria  met,  gender,  and  age  was  investigated  with the use of multiple linear regression; multicollinearity was checked by variance inflation factor, which was preferably less  than  5  to  10  for  all  covariates.  The regression analysis  was repeated after adjusting  for important Axis I diagnoses (attentiondeficit/hyperactivity disorder, simple phobias, generalized anxiety disorder, psychosis, major depressive episode, dysthymia, panic disorder, agoraphobia,  social  phobia,  obsessive-compulsive disorder, post-traumatic  stress disorder,  conduct disorder, and abuse and dependency of alcohol and substances) and subsequently with the inclusion of interactions  of  the  number  of  personality  disorder criteria met with gender and age. A mean total score for the YQOL-R was computed, and, for this study, linearly transformed so that the general quality of life index for each participant ranged from 0 to 100, with a higher score indicating a higher quality of life.

All data were entered and mostly analyzed with the use of IBM SPSS software version 20.0, with Blaker's confidence  intervals  computed  in  the  R  package BlakerCI (The R Foundation for Statistical Computing, Vienna, Austria). Graphical investigations for each disorder were created separately with the use of Microsoft Excel.

## Results

Participants

During the study enrollment period, a total of 264 adolescents (59.4% female) were referred to the Nic Waal Institute. The 63 adolescents that did not meet the  inclusion  criteria  were  excluded  due  to  mental retardation  (N  =  15,  23.8%),  need  for  immediate hospitalization (N = 19, 30.2%), inadequate fluency in the Norwegian language (N = 6, 9.5%), and the absence of the evaluator at the time of referral (N = 23, 36.5%). This left 201 adolescents eligible for the study. The attrition rate was 23.9% (N = 48) due to lack of consent from parents (N = 5, 10.4%), lack of consent from the adolescent (N = 7, 14.6%), referral being retracted before the interview (N = 6, 12.5%), not  showing  up  for  the  appointment  (N  =  11, 22.9%),  and  consent  being  retracted  during  the interview (N = 19, 39.6%).

A total  of  153  adolescents  (61.4%  female;  mean age, 15.6 years; standard deviation, 1.07) were included in the study. There were no missing data for items within the MINI, the SIDP-IV, or the YQOLR.

Table 1 shows the general distribution of personality  disorders  in  the  study  population.  The total prevalence of personality disorders was 21.6%, with  girls  having  rates  more  than  twice  as  high  as those seen in boys. Eight of the boys and 25 of the girls had at least one personality disorder ( p = .070). One of the boys and 10 of the girls had more than one personality disorder  ( p =  .052).  No  significant gender  differences  were  found  for  each  of  the personality disorders ( p ≥ .082).

Figure  1  shows  the  relationship  between  general quality  of  life  and  the  total  number  of  personality disorder  criteria  present  in  our  sample  for  each gender. No  substantial deviation from  a linear relationship was found. With linear regression analysis, the R 2  was 0.46, the variance inflation factor was  1.07  or  less,  and  no  significant  age  or  gender differences  were revealed  ( p ≥  .12),  although  there was a statistically significant relationship found with regard to the number of personality disorder criteria met (coefficient = -0.48; 95% confidence interval, 0.57  to  -0.39;  partial  eta  squared,  0.42; p <  .001). After  adjustment  for  Axis  I  disorders,  the  R 2   was 0.50,  the  variance  inflation  factor  was  1.90  or  less, and  no  significant  age  or  gender  differences  were revealed  ( p ≥  .240), although  there  was  still a significant and similar relationship found with regard to  the  number  of  personality  disorder  criteria  met (coefficient = -0.43; 95% confidence interval, -0.55 to -0.30; partial eta squared, 0.27; p < .001). There were no significant interactions between the number of personality disorder criteria met and gender and age ( p ≥ .27 without and p ≥ .075 with adjustment for Axis I disorders).

Quality of life

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TABLE 1. Prevalence of personality disorders in the sample, with 95% confidence intervals*

| Personality disorder               | Boys (N = 59) n (%) (CI*)   | Girls (N = 94) n (%) (CI*)   | Total (N = 153) n (%) (CI*)   | p value †   |
|------------------------------------|-----------------------------|------------------------------|-------------------------------|-------------|
| Paranoid                           | 0 (0.0%) (0.0%-6.1%)        | 0 (0.0%) (0.0%-3.8%)         | 0 (0.0%) (0.0%-2.3%)          | -           |
| Schizoid                           | 1 (1.7%) (0.1%-8.7%)        | 0 (0.0%) (0.0%-3.8%)         | 1 (0.7%) (0.0%-3.4%)          | 0.399       |
| Schizotypal                        | 0 (0.0%) (0.0%-6.1%)        | 0 (0.0%) (0.0%-3.8%)         | 0 (0.0%) (0.0%-2.3%)          | -           |
| Antisocial                         | 2 (3.4%) (0.6%-11.3%)       | 3 (3.2%) (0.9%-8.7%)         | 5 (3.3%) (1.3%-7.3%)          | 1.000       |
| Borderline                         | 1 (1.7%) (0.1%-8.7%)        | 7 (7.4%) (3.4%-14.6%)        | 8 (5.2%) (2.3%-9.9%)          | 0.153       |
| Histrionic                         | 0 (0.0%) (0.0%-6.1%)        | 5 (5.3%) (2.1%-11.9%)        | 5 (3.3%) (1.3%-7.3%)          | 0.166       |
| Narcissistic                       | 0 (0.0%) (0.0%-6.1%)        | 1 (1.1%) (0.1%-5.5%)         | 1 (0.7%) (0.0%-3.4%)          | 1.000       |
| Avoidant                           | 3 (5.1%) (1.4%-13.9%)       | 6 (6.4%) (2.8%-13.0%)        | 9 (5.9%) (3.0%-10.9%)         | 1.000       |
| Dependent                          | 0 (0.0%) (0.0%-6.1%)        | 1 (1.1%) (0.1%-5.5%)         | 1 (0.7%) (0.0%-3.4%)          | 1.000       |
| Obsessive-compulsive               | 0 (0.0%) (0.0%-6.1%)        | 6 (6.4%) (2.8%-13.0%)        | 6 (3.9%) (1.7%-8.2%)          | 0.082       |
| Self-defeating                     | 0 (0.0%) (0.0%-6.1%)        | 0 (0.0%) (0.0%-3.8%)         | 0 (0.0%) (0.0%-2.3%)          | -           |
| Depressive                         | 2 (3.4%) (0.6%-11.3%)       | 8 (8.5%) (3.8%-15.7%)        | 10 (6.5%) (3.4%-11.5%)        | 0.322       |
| Negativistic                       | 0 (0.0%) (0.0%-6.1%)        | 2 (2.1%) (0.4%-7.1%)         | 2 (1.3%) (0.2%-4.6%)          | 0.523       |
| At least one personality disorder  | 8 (13.6%) (1.3%-7.3%)       | 25 (26.6%) (6.0%-24.4%)      | 33 (21.6%) (15.5%-28.6%)      | 0.070       |
| More than one personality disorder | 1 (1.7%) (0.1%-8.7%)        | 10 (10.6%) (5.5%-18.3%)      | 11 (7.2%) (3.7%-12.2%)        | 0.052       |

† p value from exact chi-squared tests

FIGURE 1. Quality of life among adolescents (N = 153) who meet personality disorder criteria

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Dotted line, boys (n = 59); solid line, girls (n = 94)

Figures 2 through 5 illustrate quality of life according to the criteria met for eccentric (cluster A: paranoid, schizoid, and schizotypal), dramatic (cluster B: borderline,  histrionic,  narcissistic,  and  antisocial), fearful (cluster C: obsessive-compulsive, dependent, and avoidant), and provisional (self-defeating, depressive,  negativistic)  personality  disorders.  For each separate cluster, there was  a  tendency toward reduced quality of life with an increasing number of personality disorder criteria met.

FIGURE 2. Quality of life among adolescents who meet eccentric (cluster A) personality disorder criteria (N = 39): paranoid (n = 21), schizoid (n = 16), and schizotypal (n = 19)

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life

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65

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Figure 3. Quality of life in adolescents with dramatic (cluster B) personality disorders

FIGURE 3. Quality of life among adolescents who meet dramatic (cluster B) personality criteria (N = 70): antisocial (n = 17), borderline (n = 62), histrionic (n = 25), and narcissistic (n = 21)

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FIGURE 4. Quality of life among adolescents who meet fearful (cluster C) personality disorder criteria (N = 94): avoidant (n = 47), dependent (n = 33), and obsessive-compulsive (n = 74)

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Figure 5. Quality of life in adolescents with provisional personality disorders

FIGURE 5. Quality of life among adolescents who meet provisional personality disorder criteria (N = 107): self-defeating (n = 29), depressive (n = 78), and negativistic (n = 57)

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## Discussion

The total prevalence rate of personality disorders in the study population was 21.6%.

We  found  a  predominance  of  cluster  B  and  C disorders, which was comparable to corresponding findings from adult mental health clinic outpatients (39).

For  the  eccentric  conditions  (cluster  A),  only schizotypal personality disorder showed an approximately linear relationship between the number  of  personality  disorder  criteria  met  and general  quality  of  life.  For  the  dramatic  conditions (cluster B), there was no clear deviation from a linear relationship, especially for borderline  personality disorder, which is generally considered the prototypical dramatic personality disorder. It should also  be  noted  that  borderline  personality  disorder was the third most common personality disorder in our sample, surpassed only by depressive and avoidant personality disorder. For the fearful conditions  (cluster  C),  there  was  a  close-to-linear relationship for dependent personality disorder.

The prevalence in our study was higher than that previously  reported  for  community  samples  and lower  than  that  previously  reported  for  clinical samples  (6).  The  participants  in  the  present  study were  unselected  adolescent  outpatients  from  the general population in a defined catchment area who had been referred to a non-specialized mental health outpatient  clinic.  However,  previous  studies  have reported on samples that have a different composition  from  that  of  the  present  study.  In community samples  and  primary  care  settings,  the prevalence  numbers  for  adolescents  have  ranged from  6%  to  17%  (41).  In  samples  composed  of treatment-refractory adolescents admitted for specialized treatment (42), inpatients (4), and participants in the juvenile justice system (43-45), the prevalence numbers have ranged from 41% to 88%. Thus,  the  participants  in  the  present  study  had  a higher prevalence of personality disorder symptoms than  has  been  found  in  studies  of  community samples  and  primary  care  patients  but  a  lower prevalence than that seen in participants in studies of more severely ill patients.

As recently reviewed by Kongerslev and colleagues (6), the peak prevalence for personality disorders is reported to occur during early and middle adolescence. Studies that have focused on  late adolescence have reported lower prevalence (6,41).

In our study, the participants were mainly in mid to late adolescence.

The main finding was a relationship between the number  of  personality  disorder  criteria  met  and reduced  quality  of  life,  with  no  significant  age  or gender differences for each of the personality disorders. Our findings indicate that reduced quality of life accompanies personality disorders in adolescents in much the same way as it does in adults (26). The limited amount of data restricts the more sophisticated  analysis of  gender  differences  and personality disorder clusters.

Adjustment for the presence of Axis I diagnoses did not appreciably change the relationship between the total number of personality disorder criteria met and quality of life.

## Strengths and Limitations

Each patient was diagnosed individually with a semistructured  interview.  The  present  study  enrolled  a clinical population (i.e., adolescents who were referred to a mental health outpatient clinic). Of the 201  adolescents  eligible  for  inclusion,  153  were ultimately included. This yields a total attrition rate of 23.9% (N = 48), which is a limitation of this study.

The  cross-sectional  nature  of  the  study  makes  it difficult to infer causal relationships. The participants were included during a limited amount of time, and we do not know if there were prevalence fluctuations over time.

The study was performed at a single mental health outpatient clinic that served patients from a defined urban catchment area. Although the catchment area included a varied socioeconomic and ethnic population,  we  do  not  know  if  the  results  can  be generalized to other populations in other city districts,  more  rural  parts  of  the  country,  or  other countries or cultures.

A further possible limitation is the use of a single evaluator. The evaluator was trained by an experienced evaluator who  had  also researched personality disorders, and the two of them discussed their  ratings.  This  may  have  been  a  threat  to  the external validity of the diagnoses.

## Clinical Significance

There is an increasing focus on the benefits of the early detection and treatment of personality disorders in  adolescents.  Diagnosing  personality  disorders  in adolescents could facilitate the earlier implementation  of  adequately tailored treatment interventions and, most likely, more favorable longterm prognoses (19).

The  present  study  shows  that  quality  of  life  in adolescents is affected by the number of personality disorder  criteria  met  in  much  the  same  way  as  in adults  (26).  This  further  emphasizes  the  clinical importance  of  including  personality  disorders  and quality  of  life  assessment  in  the  general  diagnostic procedures used to treat adolescents.

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## Acknowledgements

This study has been supported by grants from the South-Eastern  Norway  Regional  Health  Authority; the Centre for Child and Adolescent Mental Health, Eastern  and  Southern  Norway;  and  Lovisenberg Diakonale Hospital.

## Disclosure of Interest

The  authors  report  no  conflicts  of  interest.  The authors  alone  are  responsible  for  the  content  and writing of this article.