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264 EFFECTS OF STRESSChapter 12Neurohormones, Neurodevelopment, andthe Prodrome of Psychosis in AdolescenceElaine F. Walker, Amanda McMillan, and Vijay MittalThe transition from childhood into adulthood is marked by significant improvementsin cognitive function, yet the adolescent capacity to inhibit responses is notmature (Luna & Sweeney, 2004), mortality rises due to risk-taking behaviors(Irwin, Burg, & Uhler Cart, 2002), and there is a gradual increase in the risk formood disorders and psychosis (Walker, 2002). At the biological level, these behavioralchanges co-occur with dramatic increases in steroid hormone secretion,and, more recently, researchers have also documented significant postpubertalmaturation of the brain.With the advent of new and noninvasive technologies for in vivo study of brainstructure and function, a window has opened on the maturation of the human brain.As a result, the biological bases for normative postpubertal behavioral changeshave come into clearer focus. At the same time, our conceptualizations of the neuralmechanisms that might subserve abnormal brain function have become more sophisticated.Contemporary research is yielding a picture of diverse and complexneuropathological processes that might give rise to the genesis of psychopathologyduring adolescence and young adulthood.It is widely recognized that there are dramatic developmental changes in clinicalexpression of vulnerability to psychosis. Most notable among these is themarked rise in risk of clinical onset in adolescence and early adulthood (Walker,2002). Numerous studies have documented that individuals who are diagnosed264