Chunk #16 — Epigenesis: The Developmental Cascade of Risk, Heterogeneity of Developmental Course, and Possible Indirect Genetic Effects on the Disinhibition Pathway
Characterizations of the developmental course of undercontrol currently remain heavily focused on continuity and cumulation of risk, not on discontinuity, which would involve transitions from higher to lower risk, or from lower to higher risk, at some point. Change in developmental course that occurs in a nonlinear trajectory--involving acceleration in risk or problem use at one time and/or drop off at another--would be one such example of the phenomenon (see, for example, the Schulenberg et al. [2005] “Fling group” trajectory, which involves both such transitions). Currently the field lacks a framework and a theory to understand these apparent discontinuities in risk level. Statistical characterization of a curvilinear trajectory or a trajectory with a quadratic component does not meet this criterion because the pathway is in reality continuity of a function with known (or determinable) rate of change. What is missing however, is a conceptual framework that can incorporate exogenous factors not predicted by prior exposure or trajectory vector. Schulenberg and colleagues' concept of developmental discontinuities (Schulenberg, Maggs, & O'Malley, 2003) and disturbances (Zucker, Wong, et al., 2006) is an early
