Abstract
The aim of this randomized controlled study is to explore the long-term efficacy of the widely used Triple P parent group training as a universal prevention intervention. 280 families with children between 3 and 6 years participated (N=l86 Triple P, N=94 control group). A multi-method assessment was conducted pre, post and one to four years after the initial assessment. To assess DSM-IV oppositional defiant disorder parents rated symptom criteria using the German CD rating scale FBB-SSV. In the long term there were small positive effect sizes for externalizing behavior. A decrease of 5.2% in prevalence rates in the Triple P group was observed. Implications are discussed, particularly for the dissemination of effective universal prevention programs.