Of the remaining 58, there were also 44 variables that were associated with either the intercepts or slopes of externalizing problems in the bivariate models, but not in the multivariate models. In these cases, the independent associations of the risk factors were too weak to be detected and their effects were statistically accounted for by other variables. Observing significant predictors in the bivariate but not multivariate models reflects collinearity among risk factors, and may reflect either a) mediation or cascade where the effects of a risk factor can be explained by more proximal causes or b) an artifact where some variables had somewhat stronger associations with externalizing problems than others, and the stronger predictors were retained over weaker predictors. Whether for mediational or artifactual reasons, some variables likely could be grouped together to reduce collinearity. For example, some non-significant parenting predictors of externalizing problems (e.g., physical harm, positive parenting) could be subsumed under other parenting variables (e.g., spanking, harsh discipline). In other cases, some risk factors may be more salient to the individual (e.g., individual stress) than others (e.g., family
