Scandinavian Journal of Psychology, 2005, 46, 145 –156 © 2005 The Scandinavian Psychological Associations/Blackwell Publishing Ltd. Published by Blackwell Publishing Ltd., 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA. ISSN 0036-5564. Blackwell Publishing, Ltd. Development and Aging Time trends in the adjustment of Swedish teenage girls: A 26-year comparison of 15-year-olds MARGIT WÅNGBY 1 , DAVID MAGNUSSON 1 and HÅKAN STATTIN 2 1 Department of Psychology, Stockholm University, Sweden 2 Department of Behavioural, Social and Legal Sciences, Örebro University, Sweden Wångby, M., Magnusson, D. & Stattin, H. (2005). Time trends in the adjustment of Swedish teenage girls: A 26-year comparison of 15-year- olds. Scandinavian Journal of Psychology, 46, 145–156. The aim of this study was to investigate stability and change over 26 years in self-reported adjustment of Swedish teenage girls. Data were collected with the same questionnaire from two school-cohorts in a middle-sized Swedish community: 522 girls attending Grade 8 (approxim- ately at age 15) in 1970, and 529 girls attending Grade 8 in 1996. The first cohort was part of the longitudinal research programme Individual Development and Adaptation (IDA). In most domains, adjustment problems were approximately as common in 1996 as in 1970, with two exceptions: more girls reported problems with self-esteem and antisocial problems in 1996. In the antisocial domain, a polarization process was indicated, with an increase also in the number of girls without adjustment problems. In the relational domains, especially peer relations, there was an increase in positive adjustment. The results are discussed in relation to earlier findings and to social changes during the period. Key words: Adjustment problems, polarization, positive adjustment, repeat study, secular change, teenage girls. M. Wångby, Department of Psychology, Stockholm University, S-106 91 Stockholm. Tel: +46 8 16 38 71; fax: +46 8 15 93 42; E-mail: mwy@psychology.su.se INTRODUCTION Since the 1990s, increasing interest has been focused on the question whether the widespread social changes during past decades have caused changes in levels of psychosocial disturbances among children and adolescents (Cohen, Slomkowski & Robins, 1999; Rutter & Smith, 1995). The identification of such changes is of high concern and has important implications for public health policies and the planning of prevention and intervention efforts. It is also essential for understanding the relation between social con- ditions and the development of psychosocial disturbances (Achenbach & Howell, 1993; Fombonne, 1995a; Verhulst, 1995). To identify and measure time trends in psychosocial dis- turbances, two main types of study designs are preferable: the prospective longitudinal study of multiple birth cohorts , which provides unbiased estimates of incidence and age of onset; and repeated cross-sectional surveys of community samples which supply time series of point prevalences for specific age groups (Fombonne, 1995). Information on time trends from these types of studies is still scarce, however (Achenbach, Dumenci & Rescorla, 2003; Rutter & Smith, 1995). Repeat surveys on substance abuse, for example, have been per- formed in the USA and in Sweden since the 1970s (Folkhälsoinstitutet and CAN, 1998; Silbereisen, Robins & Rutter, 1995). But, to our knowledge there are only a few repeat surveys that cover a broader spectrum of problems among young people. Time trends in child and adolescent behavior problems The first study that is usually cited in this connection was performed by Cederblad and co-workers in Sudanese villages near Khartoum (Cederblad, 1968; Rahim & Cederblad, 1984) between 1964 – 65 and 1979 – 80. This was a period of rapid urbanization of the area. The methodological procedures employed at each phase of the study were strictly identical: First, there was a screening of all children aged 3–15 years in the area concerning four behavior problems. Secondly, a psychiatric investigation was made of a stratified sample of children from three different symptom groups. Both in the extensive and the intensive study, the mother was inter- viewed about the children’s symptoms. The results showed that behavioral problems had increased in 1980, particu- larly among boys of school age, who were the children most exposed to the rapidly changing social conditions. Still, however, the children in the area showed remarkably low frequencies of most behavioural problems as compared with children in other (both developing and developed) countries. In the USA, a series of studies have been carried out on time trends in the problems and competences of American children and adolescents with the Achenbach System of Empirically Based Assessment (ASEBA; Achenbach & Rescorla, 2001). This series spans the 23-year period from 1976 to 1999, and makes use of both parent ratings (Achenbach & Howell, 1993; Achenbach et al. , 2003) and teacher ratings (Achenbach, Dumenci & Rescorla, 2002a) for demographically similar samples of non-referred American children aged 7–16 years