Toward a unified framework for the study of between-person and within-person structures : Building a bridge between two research paradigms

The vast majority of empirical research in the behavioral sciences is based on the analysis of between-person variation. In contrast, much of applied psychology is concerned with the analysis of variation within individuals. Furthermore, the mechanisms specified by psychological theories generally operate within, rather than across, individuals. This disconnect between research practice, applied demands, and psychological theories constitutes a major threat to the conceptual integrity of the field. Following groundbreaking earlier work, we propose a conceptual framework that distinguishes within-person (WP) and between-person (BP) sources of variation in psychological constructs. By simultaneously considering both sources of variation, it is shown how to identify possible reasons for nonequivalence of BP and WP structures as well as establishing areas of convergence. For this purpose, we first introduce the concept of conditional equivalence as a way to study partial structural equivalence of BP and WP structures in the presence of unconditional nonequivalence. Second, we demonstrate the construction of likelihood planes to explore the causes of structural nonequivalence. Third, we examine 4 common causes for unconditional nonequivalence autoregression, subgroup differences, linear trends, and cyclic trends-and demonstrate how to account for them. Fourth, we provide an empirical example on BP and WP differences in attentiveness

Immediate impact of child maltreatment on mental, developmental, and physical health trajectories

Objective: The immediate impact of child maltreatment on health and developmental trajectories over time is unknown. Longitudinal studies starting in the direct aftermath of exposure with repeated follow-up are needed. Method: We assessed health and developmental outcomes in 6-month intervals over 2 years in 173 children, aged 3-5 years at study entry, including 86 children with exposure to emotional and physical abuse or neglect within 6 months and 87 nonmaltreated children. Assessments included clinician-administered, self- and parent-report measures of psychiatric and behavioral symptoms, development, and physical health. Linear mixed models and latent growth curve analyses were used to contrast trajectories between groups and to investigate the impact of maltreatment features on trajectories. Results: Maltreated children exhibited greater numbers of psychiatric diagnoses (b = 1.998, p < .001), externalizing (b = 13.29, p < .001) and internalizing (b = 11.70, p < .001) symptoms, impairments in cognitive (b = -11.586, p < .001), verbal (b = -10.687, p < .001), and motor development (b = -7.904, p = .006), and greater numbers of medical symptoms (b = 1.021, p < .001) compared to nonmaltreated children across all time-points. Lifetime maltreatment severity and/or age at earliest maltreatment exposure predicted adverse outcomes over time. Conclusion: The profound, immediate, and stable impact of maltreatment on health and developmental trajectories supports a biological embedding model and provides foundation to scrutinize the precise underlying mechanisms. Such knowledge will enable the development of early risk markers and mechanism-driven interventions that mitigate adverse trajectories in maltreated children