Of the previously published replication attempts, our study design is most similar to that of Kim-Cohen and colleagues (2006), which assessed a community-based sample and incorporated prospective maternal and teacher reports of child outcome behavior. Furthermore, the authors constructed a continuous outcome variable that they termed a “composite mental health problem scale” that was composed of several scales from Achenbach’s Child Behavior Checklist (Achenbach, 1991). Kim-Cohen et al. used a binary measure of environmental risk that reflected more extreme levels of physical harm than used here. The authors reported significant interactions between MAOA genotype and environmental harm on both the ADHD subscale and the composite mental health scale.
