Analyzing developmental trajectories of distinct but related behaviors: A group-based method

This article presents a group-based method to jointly estimate developmenta l trajectories of 2 distinct but theoretically related measurement series. The method will aid the analysis of comorbidity and heterotypic continuity. Three key outputs of the model are (a) for both measurement series, the fo rm of the trajectory of distinctive subpopulations; (b) the probability of membership in each such trajectory group; and (c) the joint probability of membership in trajectory group.,; across behaviors. This final output offer s 2 novel features. First, the joint probabilities can characterize the lin kage in the developmental course of distinct but related behaviors. Second, the joint probabilities can measure differences within the population in t he magnitude of this linkage. Two examples are presented to illustrate the application of the method.