Chunk #12 — Epigenesis: The Developmental Cascade of Risk, Heterogeneity of Developmental Course, and Possible Indirect Genetic Effects on the Disinhibition Pathway
Another major source of imprecision in characterizing developmental course is driven by the preponderant use of methods of analysis that are variable-centered as opposed to person-centered. If the process of risk development is heterogeneous across the population, then variable-centered analysis will. at best, only crudely characterize intraindividual etiology and developmental course, and, at worst, will provide an erroneous picture. A classic study by Schulenberg and colleagues (Schulenberg, O'Malley, Bachman, Wadsworth, & Johnson, 1996) that utilized data on binge-drinking frequency in a nationally representative sample of college-age youth. illustrates this point. Their trajectory analysis identified six trajectory classes (Never, Rare, Chronic, Decreased, Increased, and “Fling”) over the 18-to-24 age interval and showed that the mean trajectory of binge drinking was not reflective of the developmental trajectories of use for any of the classes; furthermore, different predictor patterns identified membership in each of the classes. A similar pattern of developmental heterogeneity has been shown for past-year frequency of marijuana use (Schulenberg et al., 2005). Over the past decade, virtually all of the numerous trajectory class studies of adolescent-to-young-adult problem alcohol and marijuana
