Future directions in the developmental science of addictions.

This article addresses important future directions for the study of addictions, emphasizing the incorporation of developmental perspectives into how we think about substance use and disorder as unfolding processes over time and context for a heterogeneous group of individuals. These perspectives articulate complexities in the developmental processes that underlie change and continuity in human behavior over time. We consider two key developmental concepts, namely, "time" and "heterogeneity." We argue that a lack of attention to time sampling creates ambiguity in the meaning of time-linked assessments, challenges in discerning which of multiple clocks may govern behavior, and the inability in some instances to distinguish which of multiple etiological processes may be driving behavior within our samples. Moreover, artificial divisions among disorders that commonly co-occur with substance use are a barrier to the further integration of the study and treatment of addictions with that of psychopathology. Similar to recent changes in the study of psychiatric disorders more broadly, we argue that identifying common deficits among commonly comorbid disorders, rather than patterns of comorbidity per se, is key to identifying early emerging risk factors for substance use and disorder, with important implications for identifying risk populations and developmental periods as well as potentially malleable intervention targets. Attention to time sampling in theory-driven research designs and attempts to identify more homogenous groups of individuals who use and eventually abuse substances over time are two examples of ways to better understand some of the complexity underlying the development of addictions.