A behavioral scientist looks at the science of adolescent brain development

2009 Elsevier Inc. All rights reserved. In a remarkably short period of time – about 10 years, by my estimation – the developmental neuroscience of adolescence has matured from a field in its infancy to one that is now approaching its own adolescence. The papers gathered in this special issue, from some of the world’s leading scholars of adolescent brain development, showcase the richness, depth, and breadth of understanding that now characterizes this area of developmental science. As in any field that is barely a decade old, there remain many mysteries, contradictions, and unknowns. But given the short period of time during which systematic study has been ongoing, there is also a surprising degree of consistency, consensus, and replication. In this brief commentary, I focus on several broad themes that cut across the articles in this collection, both with respect to what we know (or at least have a reasonably good understanding of) and with respect to what we do not know. As a non-neuroscientist with no formal training in the study of brain development, it is beyond my expertise to delve deeply into the technical details of the research described by the contributors to this anthology. Nor is such an analysis necessary; the papers are uniformly clear and written at a level that will both interest other neuroscientists and edify behavioral scientists like myself, who increasingly find themselves needing to know about the neural underpinnings of the psychological and social phenomena they study. My focus in this commentary will be mainly on what these new studies reveal that will be of special interest to those who study adolescent behavioral development. Let me begin with what will surely strike many readers as obvious, but which needs to be said strenuously and incontrovertibly. Taken together, the contributions to this issue demonstrate conclusively that the adolescent’s brain is different from both the child’s brain and the adult’s brain. It is different with respect to both morphology and function, and at the levels of brain structures, regions, circuits, and systems. It is different with respect to grey matter (Gogtay & Thompson, this issue), white matter (Paus, this issue), structural connectivity (Schmithorst & Yuan, this issue; White et al., this issue), and neurotransmission (Doremus-Fitzwater et al., this issue; Wahlstrom et al., this issue). It is different in ways that are revealed in studies of sleep (Feinberg & Campbell, this issue), electrophysiology (Segalowitz et al., this issue), functional imaging (Luna et al., this issue; Somerville et al., this issue), pharmacological challenge (Wahlstrom et al., this issue), and stress reactivity (McCormick et al., this issue). It is different in ways that are consistent with studies of juvenile rodents (Doremus-Fitzwater et al., this issue) and non-human primates (Dahl & Forbes, this issue), and among males as well as females (Lenroot & Giedd, this issue). And it is different in ways that are consistent with the observations of behavioral scientists who study both normative development (Sebastian et al., this issue; Dahl & Forbes, this issue) and developmental psychopathology (Gogtay & Thompson, this issue). I state the obvious here to preemptively respond the claims of some non-neuroscientists that the notion of ‘‘the adolescent brain” is some sort of myth (Epstein, 2007; Males, 2009). As this collection of papers makes eminently clear, the fact that there are significant changes in the brain during adolescence is no longer debatable – if indeed it ever was. Indeed, it appears that the brain changes characteristic of adolescence are among the most dramatic and important to occur during the human lifespan. Whether neurobiological differences between adolescents and adults should inform how society treats young people is open for debate, but whether such differences are real is not (Steinberg, 2009). That said, it is important to note, as several of the contributors to this issue have stated, that ‘‘different” does not necessarily mean ‘‘deficient”; that while there are some universals in adolescent brain development, there are also important individual differences; and that the process of brain maturation in adolescence (or during any period, for that matter) unfolds within an environmental context that influences the course of neural development and moderates its expression in emotion, behavior, and cognition. It is also important to acknowledge that we currently have a better understanding of the ways in which adolescent brain development may contribute to psychopathology and problem behavior than we do of the ways in which it may contribute to normative development and positive functioning, and that researchers have paid more attention to the study of universals and processes of biological maturation than to individual differences and environmental influences. As the field matures, and as collaborations between 0278-2626/$ see front matter 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.bandc.2009.11.003 E-mail address: laurence.steinberg@temple.edu Brain and Cognition 72 (2010) 160–164