Personality Disorders in Adolescent Outpatients: a Cross-sectional Study of Prevalence, Comorbidity and Quality of Life

Personality disorders are defined as enduring and maladaptive patterns of experiencing, coping, and relating to others. In DSM-IV as well as ICD-10, personality disorders may be diagnosed in adolescents when the individual’s maladaptive personality traits are pervasive, persistent, and unlikely to be limited to a particular developmental state or an episode of an Axis I disorder. Research supports the assumption that pathological personality traits emerge at an early age and are related to health-risk behaviors in adolescence as well as young adulthood. In recent years there has been an increasing focus on the valid existence of personality disorders in adolescents, as well as on the prognostic importance of diagnosing these for the most part long-lasting and agonizing disorders as early as possible. Personality disorders are common conditions, with prevalences of about 13% in the general adult population, up to 40% in adult outpatient samples, and up to 71% in adult inpatient samples. In adolescents, prevalences range from 6% to 17% in community samples, and in inpatient and more severely ill outpatient samples from 41% to 88%. There are few, if any, reports on the prevalence in less severely ill adolescents who have been referred to general service outpatient clinics. Previous studies on adults have shown that the number of personality disorder symptoms is negatively correlated to general functioning and quality of life, and that personality disorders are associated with an extensive Axis I comorbidity, such as mood, anxiety, and substance abuse disorders. Objectives: The main objective of this thesis was to study the prevalence of personality disorders and clinically relevant Axis I comorbidity, in an unselected sample of adolescents who were referred to a non-specialized (general service) child and adolescent outpatient clinic. The more specific aims were: - To investigate the relationship of personality disorder symptoms, i.e. the number of personality disorder diagnostic criteria met by the adolescents, with self-perceived quality of life (paper I). - To investigate the co-occurence of personality disorders and common Axis I disorders in adolescents with ADHD, including possible gender differences (paper II). - To investigate the relationship between alcohol and substance use disorders and personality disorders in the referred adolescents, with special regard to gender differences (paper III). Material and methods: The three studies included in this thesis are based on an outpatient clinical sample, consisting of 153 adolescents (94 girls, 59 boys), aged 14 to 17 years. 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 covering broad aspects of quality of life. ADHD, conduct disorder and other Axis I conditions were assessed using the Mini International Neuropsychiatric Interview (MINI). All assessment work was done by the author of this thesis. Results: The girls in our study were overall more severely ill than the boys, with higher prevalences of personality disorders as well as Axis I disorders. We found that 21.6% of the adolescents fully met the diagnostic criteria for at least one personality disorder. No significant gender differences in the prevalence of each of the personality disorders were revealed. Practically all adolescents with a personality disorder had one or more Axis I disorders. Quality of life was negatively related to the number of personality disorder criteria met: this finding was comparable to what has previously been reported in adults. Adjustment for the presence of Axis I disorders did not appreciably affect these findings. More than two thirds of the adolescents met the criteria for at least one Axis I disorder, with significantly more mood and anxiety disorders in girls than in boys. A total of 13.7% of the adolescents met diagnostic criteria for ADHD, with no significant gender difference; 17.6% had conduct disorder, and 4.6% had both ADHD and a personality disorder. There was a significantly elevated number of personality disorder symptoms in adolescents with ADHD diagnosis, and this relationship was not significantly weakened when adjusted for age, gender and other Axis I disorders. Antisocial and borderline personality disorders were significantly more frequent in girls than in boys with ADHD. With regard to substance use disorders, 18.3% of the adolescents had either alcohol or cannabis abuse or dependency, also with no significant gender difference. There was a strong association between number of personality disorder symptoms and having one or more substance use disorders; this relationship was not significantly changed by adjustment for gender, age and presence of Axis I disorders. For boys, no significant associations of substance use disorders and specific personality disorders, conduct disorder, or ADHD were found. For girls, there were significant associations of substance use disorders and borderline personality disorder, negativistic personality disorder, having more than one personality disorder, conduct disorder, and ADHD. Conclusions: As expected, the adolescents in our study had more personality disorders than what has been previously found in studies on community samples and primary care patients, but less than in studies on more severely ill outpatients and inpatients. We found the same association as previously reported from studies on adults between personality disorder symptoms and quality of life. This supports the importance of evaluating quality of life when focusing on early detection and treatment of personality disorders in adolescents. ADHD, conduct disorder, antisocial personality disorder and substance use disorders were equally prevalent in both genders. This suggests that ADHD and possibly conduct disorder may be more prevalent than previously assumed in adolescent girls. In girls with ADHD, antisocial and borderline personality disorders were significantly more frequent than in boys. This highlights the importance of assessing antisocial and borderline personality pathology in adolescent girls presenting with ADHD symptoms. The highly significant association between the number of personality disorder symptoms and substance use disorders, regardless of adjustment for gender and Axis I comorbidity, suggests that having a personality disorder in itself may constitute a risk factor for developing substance use disorders in adolescence