Not much is known about neurodevelopmental factors involved in the pathophysiology of child and adolescent depression. Neuroendocrine and sleep EEG research paradigms have been used in the majority of published studies examining the neurobiological correlates of early-onset depression. Although these procedures have their merits, the “window to the brain” afforded by these methods is extremely limited. Emerging neuroimaging technologies will provide a unique opportunity to investigate the brain mechanisms underlying child and adolescent depression. To date, however, the application of these techniques in the study of early-onset depression is in its infancy.

The existence of major depressive disorder (MDD) in children and adolescents was controversial until relatively recently, and the diagnosis of MDD was not included in any child psychiatric text prior to the late 1970s (Puig-Antich & Gittleman, 1982). Research over the past two decades, however, has clearly demonstrated that children are capable of experiencing episodes of depression which meet standard DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th ed.) criteria for MDD (Birmaher et al., 1996c; Ryan et al., 1987). In addition, MDD in children and adolescents is common, recurrent, and associated with significant morbidity and mortality (Birmaher et al., 1996c). Epidemiological studies estimate that the prevalence of depression is 2 percent in children (Kashani et al., 1983) and 5–8 percent in adolescents (Lewinsohn, Clarke, Seeley & Rohde, 1994).