 Mediation analysis will be conducted using a growth-curve framework implemented in an SEM. Models will be constructed by first fitting growth models for mediators and outcomes and then fitting mediational growth models. Investigators will follow the same sequence described above for establishing the best model of longitudinal change for Aim 1. Latent growth models will be comprised of at least two latent factors; one factor will represent the initial status, and one or more factors will represent the growth rate of a variable, where more than one factor will be required in the event of non-linear change e.g., a quadratic term. Mediation will be examined following recommendations by MacKinnon 2008 for assessing mediation in the growth models context. The growth factor of the mediator will be regressed on the initial status of the mediator, the outcome, and the intervention group. A significant effect for the intervention group establishes a relation between the intervention group and the mediator, controlling for baseline levels of the mediator and outcome. Next, the growth factor will be regressed on the initial status of the mediator, the outcome, the slope of the mediator, and the intervention group. A significant effect of the mediator growth factor establishes a relation between change in the mediator and change in the outcome, controlling for baseline levels of the mediators and outcome. 