ABSTRACT
In this chapter, we focus on analysis of longitudinal data. Unlike crosssectional studies taking a single snapshot of study subjects at a particular time point, individuals in longitudinal or cohort studies are followed up for a period of time, with repeated assessments during the follow-up time. By taking advantages of multiple snapshots over time, longitudinal studies have the ability to capture both between-individual differences and within-subject dynamics, permitting the study of more complicated biological, psychological, and behavioral processes than their cross-sectional counterparts.
