On the basis of the extant literature, we hypothesized that: (1) youths with ADHD would have smaller basal ganglia structures, including the caudate and putamen; (2) youths with BP would have reduced limbic structures, including hippocampal and amygdala volumes, and enlarged right nucleus accumbens volumes; (3) youths with co-morbid BP and ADHD would have limbic abnormalities similar to youths with BP alone and would have smaller basal ganglia structures similar to youths with ADHD

An emerging neuroimaging literature indicates that distinct subcortical brain structures may characterize ADHD and BP in youths.

youths with BPD were hypothesized to have reduced callosal growth in posterior regions.

We hypothesized that (1) posterior callosal volumes would be reduced in youths with BPD given that these structures are rapidly maturing during childhood and adolescence and as a result may be more vulnerable during this time of significant brain myelination and pruning, particularly around the time of illness onset; (2) consistent with the hypothesized role of the prefrontal cortex in mood dysregulation and cognitive abnormalities in BPD (Soares and Mann 1997; Wilder-Willis et al. 2001), genual volume was expected to be abnormal (i.e., smaller) in youths with BPD; and (3) consistent with Brambilla and colleagues’ findings, there would be an absence of typical age-related changes in specific callosal volumes in youths with BPD (Brambilla et al. 2003).

The present study represents the first application of a comprehensive set of measures that permit the comparison of total CC and callosal subregion areas and volumes in youths with BPD and HC.

we predicted that there would be diagnosis-by-sex interactions in subcortical structures rich in sex hormone receptors, particularly in the amygdala and hippocampus.

we predicted, based on previous reports, that youths with BPD would have abnormal NA volumes22,23 and that youths with SZ would have reduced thalamic volumes.24,33 We also predicted that the BPD with psychosis group would share features with the BPD without psychosis and the primary psychotic disorder groups

we hypothesized that reduced amygdala volume would more reliably be associated with BPD and reduced hippocampal volume with SZ.

we set out to compare youths with early-onset BPD without psychosis and BPD with psychosis to those with SZ to discern if there would be findings in the amygdala and the hippocampus that would differentiate these disorders.