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The Role of Preventive Interventions 455of research linking children’s social experience to both temporary and permanentalterations in the structure and function of the brain (Beers & De Bellis, 2002;Cicchetti, 2002; De Bellis, Keshavan, Spencer, & Hall, 2000; Ito, Teicher, Glod,& Ackerman, 1998; Landry, Miller-Loncar, Smith, & Swank, 2002; McEwen,1997; Sapolsky, 1996; Stein, Koverola, Hanna, Torchia, & McClarty, 1997). Someof this research examines the effects of stressful experiences and its potentiallydeleterious effects on executive function. Cortisol, a glucocorticoid hormone producedby the hypothalamic-pituitary-adrenal (HPA) axis in response to stress, islinked to the modulation of long-term neuronal changes in cognition and behavioroccurring in response to psychological stress. Chronic elevations in cortisolare associated with hippocampal atrophy and with learning and memory deficitsboth in humans and nonhuman animal models (McEwen & Sapolsky, 1995). It islikely that chronic stress throughout childhood and adolescence impacts braindevelopment in ways that interfere with the normal development of executivefunction. Research has shown that children with posttraumatic stress disorderexhibit lower neural integrity in the anterior cingulate (De Bellis, Keshavan, Spencer,& Hall, 2000) and poorer executive function (Beers & De Bellis, 2002).Effective regulation of the physiological response to stress, in other words,moderate increase followed by downregulation, is important for cognitive functionsassociated with the prefrontal cortex (Erickson, Drevets, & Schulkin, 2003).As shown in adults, indicators of effective regulation of stress associated with notonly HPA axis function (Lupien & McEwen, 1997) but also with sympatheticadrenalmedullary (SAM) function have been shown to significantly correlate withattentional processes (Skosnik, Chatterton, & Swisher, 2000). Similarly, effectiveregulation of the HPA axis response to stress has been associated with executivefunction and behavioral self-regulation abilities as early as the preschool years(Blair, Granger, & Razza, 2005). To the extent that preventive interventions canhelp teens reduce the incidence of stress exposure, develop greater awareness oftheir level of stress, and learn skills (mindfulness, relaxation or emotion regulationtechniques) that reduce such stress, impacts may be shown on both brain andbehavior.Implications and Future DirectionsAlthough a comprehensive model for the development of adolescent problembehavior does not exist, research is beginning to elucidate the importance ofneurocognitive function as one component in an integrated, developmental model.The time course in the morphological development of the frontal lobes suggeststhe importance of timing in preventive interventions throughout childhood andearly adolescence. It is now evident that the frontal lobes and the networks connectingthem to the limbic system maintain an ability to restructure throughout