How do outcomes in a specified parent training intervention maintain or wane over time?

In a randomized prevention trial, 238 recently separated mothers and their young sons were assigned to either Parent Management Training (PMT) or a comparison group. Families were intensively assessed at baseline and at each 6-month interval through 30 months. To understand the effects of PMT, we first evaluated effect sizes among family variables over time. Second, because observed parenting was the target of PMT, we hypothesized a sequential pattern of structured changes within and between individuals. Using constructs with mismatched sources of data, we conducted a set of latent growth mediational analyses to test hypothesized mechanisms explaining change. Effect sizes indicated that parenting changed first within 12 months, followed by changes in boy behaviors and finally changes in maternal depression within 30 months. Unique follow-up findings indicated that intervention effects on reductions in maternal depression were mediated by reductions in boy externalizing; intervention effects on externalizing were mediated by reductions in boy depression. As expected, increases in effective parenting predicted reductions in child behavior problems. PMT effects on internalizing were direct and indirect, partially mediated by parenting practices. Results are discussed from a system's perspective on PMT amplifiers.