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Early-Onset Bipolar Disorder 321United States of 3–7% (K. D. Chang, 2000). In one academic child psychiatryclinic, cross-sectional assessment found only 12% of children with ADHD to alsohave BD (Biederman et al., 1996). Irritability is furthermore often associated withuncomplicated ADHD (American Psychiatric Association, 1994). Thus, it is unlikelythat most children with ADHD, and just irritability, will develop BD, butclearly some of them do. Similarly, although rates of conversion from depressionto BD during childhood are estimated to be 20–30% (Geller et al., 1994), 70–80%of children with depression will not experience a manic episode. Thus, the sensitivityof using these symptom complexes is high, but the specificity relatively low.Adding a family history of BD, for example, a first- or second-degree relative withBD would increase the specificity, but it is unclear by how much. Children ofparents without BD can still develop BD, so inclusion of a first-degree relativewith BD as a required risk factor overlooks these children.Personality or temperament traits may add further clues. We found that bipolaroffspring having both parents with a mood disorder, and thus believed to be ateven higher familial risk for BD, had higher levels of rejection sensitivity, a lackof mood reactivity (self-soothing capability), and overall more severity of irritabilityand depressed mood (K. D. Chang et al., 2000). Offspring with psychiatricdisorders were considered to have had less flexibility, less task orientation, andfewer periods of good mood compared to those without disorders (K. D. Chang,Blasey, Ketter, & Steiner, 2003). Other key symptoms that may appear before fullmania include hyperactivity and hypersexuality (Geller & Luby, 1997).Biological Markers of Risk for BipolarDisorder DevelopmentDespite these phenomenological findings, there is still significant uncertainty. Biologicalmarkers that are linked specifically to BD are needed to lessen doubt of riskfor BD development. It is now widely agreed upon that numerous psychosocialfactors, including life stress and family environment, act together with genetic predispositionto create BD (Post, Leverich, Xing, & Weiss, 2001). This genetic predispositionis likely reflected in brain characteristics, such as regional gray mattervolume, local neurotransmitter receptor density and sensitivity, and preferentialneural circuitry used in affective situations. Identification of the brain characteristicsmost highly associated with BD development, along with the genetic factorsthat affect their development, could lead to early identification of those at highestrisk for BD development and a better understanding of the pathophysiology of BD.Neuroimaging Findings in Bipolar DisorderMagnetic resonance imaging (MRI) studies in adults with BD have found assortedglobal cortical abnormalities, including aberrant total brain volume, lobar volume,