Although most parent training programs produce positive effects, about one third of the children still show conduct problems at clinical levels after treatment.

In the present study, predictors and mediators of treatment non-response among children aged 4-8 years were investigated one-year after treatment with the Incredible Years parent training program (PT), or combined parent training and child treatment (PT+CT) in a randomized controlled trial. The study was conducted in two university cities in Norway.

KIDDIE-SADS, Eyberg Child Behavior Inventory (ECBI), Child Behavior Checklist (CBCL), Parent Practices Interview (PPI), Parent Stress Index (PSI), Preschool Behavior Questionnaire (PBQ), Teacher Report Form (TRF), were used.

Before treatment all children fulfilled the criteria for an ODD diagnosis or a sub-threshold diagnosis. At the one-year follow-up 33 % of the treated children still showed such a diagnosis, and they were defined as treatment non-responders.

Both family and child variables predicted treatment non-response at the one-year follow-up, although being involved with the child protection services was found to be the strongest predictor in multivariate analysis. Pretreatment child characteristics predicting treatment non-response at the one-year follow-up were high levels of child internalizing and aggression problems as reported by mothers. Further, mothers of children still showing a ODD diagnosis at the one-year follow-up, reported less change in negative parenting practices as compared to mothers of treatment responders.