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Working memory (WM) deficits have been shown to be associated with core ADHD symptoms, worse academic achievement and peer-relationship problems. Internalizing symptoms, such as anxiety and depression, have also been associated with impaired WM performance. However, the association of anxiety and depression and WM performance remains unclear for children and adolescents with ADHD. Further, it is unknown how these comorbid conditions might affect WM performance in the two main ADHD subtypes. The association of anxiety and depression and the specific components of spatial (SWM) and verbal working memory (VWM) were examined in 303 children and adolescents with ADHD, combined type (ADHD-CT) and 77 ADHD, inattentive type (ADHD-IA) compared to 128 age- and gender-matched typically developing participants. The relationship between anxiety and depression and WM was assessed using multiple linear regression analyses and separate simple regression analyses. Higher levels of anxiety/depression were associated with (1) increased between-search errors in the typically developing participants alone, (2) a better strategy performance in the ADHD-CT group, and (3) a better spatial span performance in the ADHD-IA group. VWM was equally impaired in the ADHD-CT and ADHD-IA groups, independent of the levels of anxiety and depression. The results suggest that the effects of internalizing symptoms on WM differ in typically developing children and adolescents compared to those with ADHD. Further, high levels of anxiety and depression modified WM performance differently according to the specific ADHD subtypes. This might help explain contradictory findings observed in previous studies of mixed samples of participants with ADHD-CT and ADHD-IA. [ABSTRACT FROM AUTHOR]

Pediatric bipolar disorder (BD) and unipolar disorder (UD) share common symptomatic and functional impairments. Various brain imaging techniques have been used to investigate the integrity of brain white matter (WM) and gray matter (GM) in these disorders. Despite promising preliminary findings, it is still unclear whether these alterations may be considered as common trait markers or may be used to distinguish BD from UD. A systematic literature search of studies between 1980 and September 2013 which reported WM/GM changes in pediatric and adolescent BD/UD, as detected by diffusion tensor imaging and voxel-based analysis was conducted. Of the 34 articles judged as eligible, 17 fulfilled our inclusion criteria and were finally retained in this review. More abnormalities have been documented in the brains of children and adolescents with BD than UD. Reductions in the volume of basal ganglia and the hippocampus appeared more specific for pediatric UD, whereas reduced corpus callosum volume and increased rates of deep WM hyperintensities were more specific for pediatric BD. Seminal papers failed to address the possibility that the differences between unipolar and bipolar samples might be related to illness severity, medication status, comorbidity or diagnosis. UD and BD present both shared and distinctive impairments in the WM and GM compartments. More WM abnormalities have been reported in children and adolescents with bipolar disease than in those with unipolar disease, maybe as a result of a low number of DTI studies in pediatric UD. Future longitudinal studies should investigate whether neurodevelopmental changes are diagnosis-specific. [ABSTRACT FROM AUTHOR]