Thesis (Ph. D.)--University of Rochester. Dept. of Clinical and Social Sciences in Psychology, 2012.Although some progress has been made in applying the concept of family boundaries to understand triadic family functioning, researchers continue to define family dynamics largely on the basis of the form or physical characteristics of a set of behaviors or processes. Consequently, relatively little attention has been devoted to elaborating on the function of behaviors within the context of triadic family relationships. To bridge this gap in the field, this study examined the developmental and incremental utility of a novel triadic observational system that captures both the form and function of family interactions characterized by cohesion, enmeshment, and disengagement. Accordingly, family cohesion, enmeshment, and disengagement were examined as predictors of a host of adolescent adjustment factors in a sample of 275 fathers, mothers, and adolescents (M age = 12.6 years). The whole family participated in a family problem solving task to assess family boundary processes. Both parents, adolescents, and teachers reported on adolescents' adjustment problems across two annual waves of assessment. Demonstrating some support for the incremental utility of a boundary conceptualization of triadic family relationships, results of autoregressive structural equation modeling indicated that coder ratings of family cohesion uniquely predicted lower levels of adolescent adjustment difficulties concurrently and prospectively while enmeshment uniquely predicted greater adolescent adjustment difficulties at the first assessment occasion and over time after taking into account broad indices of family functioning (i.e., positive affect, negativity and conflict) and family structural characteristics (i.e., birth order, number of siblings). Family disengagement, on the other hand, was not a unique predictor of adolescent adjustment but negativity and conflict was. The results are discussed in relation to the complementary role cohesion and enmeshment play in adolescents' developmental trajectories as well as various explanations for the lack of significant findings involving family disengagement (e.g., poor face validity of the disengagement construct)