Children with Mild to Borderline Intellectual Disabilities and Externalizing Behavior: Individual Characteristics, Family functioning and Treatment Effectiveness

Children with mild to borderline intellectual disabilities (MBID; IQ between 55 and 85 with problems in adaptive functioning) have been found to show higher rates of emotional and externalizing behavior problems and their externalizing behavior problems tend to persist over time, more so than those in peers with average intelligence (defined here as an IQ above 85). The processes underlying these externalizing behavior problems in children with MBID nevertheless largely remained unclear and evidence-based interventions aiming to reduce externalizing behavior problems in children with MBID were lacking. The aim of this dissertation was twofold. First, we obtained insight into the characteristics of children with MBID and externalizing behavior and their parents. We therefore conducted cross-sectional studies on parenting behavior, the parent-child relationship, and children’s executive functions and social information processing in comparison to children with MBID with less behavior problems. Second, we evaluated the effectiveness of combined parent-management training and child cognitive behavior therapy (Standing Strong Together), aiming to reduce externalizing behavior problems in 9-16 year old children with MBID, by means of a cluster randomized controlled trial. Results of Standing Strong Together combined with Care as Usual (CAU) (n=97) in the intervention condition, were compared to results of CAU alone in the control condition (n=72). First, the results suggest tentative evidence for the association between executive functions and the occurrence of externalizing behavior problems, as children with externalizing behavior problems show more deficits on working memory tasks. Second, social information processing in children with MBID and externalizing behavior problems was found to differ from children with MBID without such problems, with the former generating more aggressive and fewer assertive responses, and selecting fewer assertive responses. We may carefully conclude that both EF and SIP need to be considered when explaining the occurrence of externalizing behavior problems in children with MBID. Third, parents of children with externalizing behavior problems showed less positive parenting and more negative parenting, and a less positive parent-child relations, compared to parents of children without such accompanying problems. The parent-child relationship was most strongly associated with externalizing behavior problems in children with MBID. Fourth, Standing Strong Together led to a significant benefit on teacher reported but not on parent reported externalizing behavior problems. Standing Strong Together had significant effects on parent rated positive parenting and significantly improved the parent rated quality of the parent-child relationship. In conclusion, the results presented in the current dissertation underscore the importance of understanding externalizing behavior problems in children with MBID. Besides differences in social information processing and parenting behavior between children with MBID with and without externalizing behavior problems, the importance of including executive functioning and the parent-child relationship in the understanding of externalizing behavior problems was demonstrated. Performing a randomized controlled trial and parent-child intervention aiming to reduce externalizing behavior problems in children with MBID appeared feasible and indicated positive effects. In response to the results presented in the current dissertation, Standing Strong Together may be implemented in daily clinical practice and further developed based on the knowledge we now have.