Scandinavian Journal of Psychology, 2008 DOI: 10.1111/j.1467-9450.2008.00700.x © 2008 The Authors. Journal compilation © 2008 The Scandinavian Psychological Associations. 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 Health and Disability Parent training for young Norwegian children with ODD and CD problems: Predictors and mediators of treatment outcome STURLA FOSSUM, 1 WILLY-TORE MØRCH, 1 BJØRN H. HANDEGÅRD, 1 MAY B. DRUGLI 2 and BO LARSSON 2 1 Centre for Child and Adolescent Mental Health, Department of Clinical Medicine, University of Tromsø, Norway 2 Section of Child & Adolescent Mental Health, Norwegian University of Science and Technology, Norway Fossum, S., Mørch, W.-T., Handegård, B. H., Drugli, M. B. & Larsson, B. (2008). Parent training for young Norwegian children with ODD and CD problems: Predictors and mediators of treatment outcome. Scandinavian Journal of Psychology. Participants were 121 children, aged 4–8 years referred for conduct problems, and their mothers. A parent training intervention was implemented in two outpatient clinics in Norway. Treatment responders were defined as children scoring below a cut-off on the Eyberg Child Behavior Inventory, a score below an optimal cut-off for children in day-care and school as reported by teachers, in addition to a 30% reduction or greater in observed negative parenting. Self-reported parenting practices were explored as potential mediators. The results of logistic regression analyses showed that high levels of maternal stress, clinical levels of ADHD, and being a girl predicted a poorer outcome in conduct problems at home, while pretreatment clinical levels of ADHD predicted a poorer outcome as perceived by the teachers. Harsh and inconsistent parental disciplining emerged as significant partial mediators of changes in conduct problems, highlighting the importance of altering parenting practices to modify young children’s conduct problems. Key words: Conduct problems, predictors, mediators, parent training. Sturla Fossum, Centre for Child and Adolescent Mental Health, Department of Clinical Medicine, University of Tromsø, NO-9037 Tromsø, Norway. E-mail: sturla.fossum@fagmed.uit.no INTRODUCTION Disruptive behavior disorders including oppositional defiant disorder (ODD) and conduct disorder (CD) are among the most common reasons for referring children and adolescents to outpatient treatment in child and adolescent psychiatric clinics in Norway (Anderson, Halsteinli, Kalseth, Pedersen & Waagan, 2002). Children with ODD or CD are at risk of developing a variety of problems such as peer rejection, school failure, psychopathology, substance abuse and criminality (Burke, Loeber & Birmaher, 2002). Because of the stability of child aggressive behaviors, disruptive behavior disorders constitute a major health problem (Simonoff, Elander, Holmshaw, Pickels, Murray & Rutter, 2004). While several effective interventions have been developed for children and adolescents (Fonagy & Kurtz, 2002), parent training seems to be the treatment of choice for young children (Brestan & Eyberg, 1998; Fossum, Handegård, Martinussen & Mørch, 2008). The main focus of parent training is to help parents alter their child’s behavior by teaching them to use more appropriate and positive parenting practices. Introducing an evidence-based parent training intervention in Norway, the Incredible Years program (IY; Webster-Stratton & Reid, 2003a), predictors and mediators related to outcome are of particular interest in evaluation of treatment effects. Mediation effects refer to the feasible underlying processes of change in treatment, or mechanisms of action. Weersing and Weisz (2002) noted a lack of studies exploring mechanisms of change in studies applying parent training interventions. Changes in parenting practices may serve as mediators in parent training and cause changes in child conduct problems. Some studies of the IY program have explored mediating effects of parenting practices. In the US, Beauchaine, Webster-Stratton and Reid (2005) reported that reductions in inconsistent and harsh child disciplining mediated treatment outcome in a study pooling data from six independent clinical trials. In a replication of the IY in the UK, Gardner, Burton and Klimes (2006) further noticed that changes in positive parenting skills significantly mediated changes in child conduct problems. In a recent meta-analysis of predictors in parent training, low family income resulted in a large standardized effect size, while variables such as low educational level/occupation, maternal psychopathology and severe pretreatment child behavior problems produced moderate effect sizes (Reyno & McGrath, 2006). These findings indicate that such variables influence treatment outcome negatively. Maternal age has also been identified as a significant predictor of treatment outcome in IY in the sense that children with mothers with median age above 35 experienced less reduction in conduct problems compared to children with younger mothers (Beauchaine et al., 2005). In addition to the variables identified in meta-analyses the following are important: ODD and CD comorbidity with other diagnoses, and the co-occurrence of ODD/CD with Attention Deficit Hyperactivity Disorder (ADHD), anxiety or depression is particularly high (Angold, Costello & Erkanli, 1999). ADHD