The Development of Personality Extremity From Childhood to Adolescence: Relations to Internalizing and Externalizing Problems Alithe L. Van den Akker, Peter Prinzie, and Maja Dekovi´ c Utrecht University Amaranta D. De Haan Ghent University Jessica J. Asscher University of Amsterdam Thomas Widiger University of Kentucky This study investigated the development of personality extremity (deviation of an average midpoint of all 5 personality dimensions together) across childhood and adolescence, as well as relations between personality extremity and adjustment problems. For 598 children (mean age at Time 1 = 7.5 years), mothers and fathers reported the Big Five personality dimensions 4 times across 8 years. Children’s vector length in a 5-dimensional configuration of the Big Five dimensions represented personality extremity. Mothers, fathers, and teachers reported children’s internalizing and externalizing problems at the 1st and final measurement. In a cohort-sequential design, we modeled personality extremity in children and adolescents from ages 6 to 17 years. Growth mixture modeling revealed a similar solution for both mother and father reports: a large group with relatively short vectors that were stable over time (mother reports: 80.3%; father reports: 84.7%) and 2 smaller groups with relatively long vectors (i.e., extreme personality configuration). One group started out relatively extreme and decreased over time (mother reports: 13.2%; father reports: 10.4%), whereas the other group started out only slightly higher than the short vector group but increased across time (mother reports: 6.5%; father reports: 4.9%). Children who belonged to the increasingly extreme class experienced more internalizing and external- izing problems in late adolescence, controlling for previous levels of adjustment problems and the Big Five personality dimensions. Personality extremity may be important to consider when identifying children at risk for adjustment problems. Keywords: Big Five personality, personality structure, growth mixture modeling, internalizing problems, externalizing problems The validity of the Big Five approach for describing child and adolescent personality has been well established (Mervielde, De Clercq, De Fruyt, & Van Leeuwen, 2005; Shiner & Caspi, 2003; Tackett, 2006). Results have indicated that the Big Five framework applies to children and adolescents in much the same way as it does to adults, making it possible to study the development of personality across the life span within a single framework. Fur- thermore, the Big Five approach has proven useful in predicting many child outcomes, including child adjustment problems. Chil- dren who are low on agreeableness and conscientiousness are prone to externalizing problems (Lynam et al., 2005; Ozer & Benet-Martinez, 2006; Prinzie, Van der Sluis, De Haan, & Dek- ovi´ c, 2010; van den Akker, Dekovi´ c, & Prinzie, 2010), whereas introverted and emotionally unstable children are at risk of devel- oping internalizing problems (De Pauw & Mervielde, 2010; Van Leeuwen, Mervielde, Braet, & Bosmans, 2004). While the five-factor model was originally developed to de- scribe normal personality, the potential utility of the dimensional approach for understanding problematic personality in adults (Samuel & Widiger, 2008; Trull & Durrett, 2005; Widiger, 2011), as well as in children and adolescents (De Clercq, De Fruyt, Van Leeuwen, & Mervielde, 2006; Mervielde et al., 2005), is becoming apparent. Indeed, for the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Associ- ation, 2013), a dimensional approach to personality pathology has been advocated as an integrative framework that may be included as an alternative to the diagnostic criteria for different personality disorders that often result in a high comorbidity among persona- lity disorders and in a high incidence of a diagnosis of personality disorder “not otherwise specified.” This proposed dimensional trait model represents an extension of the five-factor model (American Psychiatric Association, 2013) although there is some disagree- Alithe L. Van den Akker, Peter Prinzie, Maja Dekovi´ c, Department of Child and Adolescent Studies, Utrecht University, Utrecht, the Nether- lands; Amaranta D. De Haan, Department of Developmental Psychology, Ghent University, Ghent, the Netherlands; Jessica J. Asscher, Research Centre for Forensic Child and Youth Care Studies, University of Amster- dam, Amsterdam, the Netherlands; Thomas Widiger, Department of Psy- chology, University of Kentucky. Correspondence concerning this article should be addressed to Alithe L. Van den Akker, who is now at the Department of Child Development and Education, University of Amsterdam, Nieuwe Prinsengracht 130, 1018 VZ Amsterdam, the Netherlands. E-mail: a.l.vandenakker@uva.nl This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Journal of Personality and Social Psychology © 2013 American Psychological Association 2013, Vol. 105, No. 6, 1038 –1048 0022-3514/13/$12.00 DOI: 10.1037/a0034441 1038