Disentangling pediatric bipolar disorder and attention deficit-hyperactivity disorder: A neuropsychological approach

The clinical and diagnostic debate circulating pediatric bipolar disorder (PBD) has been highlighted as one of the most controversial themes in child psychiatry. With atypical symptomatic expression, constituting its predominant diagnostic discrepancy, PBD is manifested through prolonged manic episodes and affective storms, lacking the symptomatic cycling and episodic nature presented in adult BD. Apart from its unique clinical presentation, the substantial symptomatic overlap with attention deficit hyperactivity disorder (ADHD) indicate an important diagnostic challenge in PBD. Specifically, both disorders share core characteristics such as irritability, hyperactivity, excessive talking and distractibility. Against this background of findings on the overlapping symptomatology between PBD and ADHD, current research guidelines highlight the need of exploring non-symptomatic markers as potential clinical phenotypes. Especially in disorders with distinctive biologic underpinnings, both clinicians and researchers have shown increased interest in establishing neuropsychological profiles. Recent neuropsychological studies indicated the distinct nature of neurocognitive deficits in PBD, describing impairments in various cognitive skills during acute episodes phases, while this severe deterioration of cognitive deficits appears to persist even during euthymic states. Regarding neuropsychological assessment in AHD, recent findings suggested dysfunctions in the domains of working memory, verbal memory and response inhibition. Furthermore, neuroimaging studies are fast becoming a key instrument to establish distinct neuropsychological profiles for PBD and ADHD. A large number of neuroimaging studies have indicated abnormalities in limbic, cortical and subcortical brain systems, while meta-analytic findings of voxel based morphometric studies highlight abnormalities in dorsolateral and lateral orbitofrontal-temporal areas in PBD. In recent neuroimaging findings with focus on neurocognitive performance during an emotional Stroop task, patients diagnosed with ADHD indicated activation on higher cortical centres associated with processing speed and significantly decreased role of sustained attention. Furthermore, these findings suggest emotional regulation and inhibitory control are moderately intercorrelated, adding more complexity to the theme of neurocognitive deficits in ADHD. These observations on the neurobiological mechanisms of cognitive impairments in PBD appear to provide robust evidence on a potential specific neuropsychological profile of PBD, the relationship between mood states and neuropsychological functioning, and the link between emotion generation and regulation in children with PBD.