(BD) is a chronic, complex
mood disorder that has been increasingly diagnosed in children in recent years (Youngstrom et al. 2005
; Blader and Carlson 2007
; Moreno et al. 2007
) and is associated with poor prognosis and outcome (Goodwin and Jamison 2007
). The pediatric phenotype pediatric bipolar disorder (PBD), with illness onset before age 18, may represent an especially genetically driven form of the disorder (Lin et al. 2006
; Rende et al. 2007
) and is associated with increased risk of suicide and substance abuse, above and beyond levels of risk seen in BD in general (Lin et al. 2006
), as well as behavioral, academic, social, and legal problems (Birmaher 2007
). Poor outcomes have been demonstrated longitudinally in domains such as treatment response, recovery rates, and relapse rates; these outcomes are similar to those seen in adults with severe, treatment-resistant BD (Geller et al. 2000
; Geller et al. 2001
). Additionally, rates of hospitalization and psychosis in youths with BD are elevated (Birmaher and Axelson 2006
), and nearly one third of youths with BD have a lifetime history of attempting suicide (Goldstein et al. 2005
Understanding the phenomenology of PBD remains a challenge for the field. The potential cognitive and neuropsychological deficits experienced by these youths has been attracting increasing amounts of attention. Understanding cognitive abnormalities in PBD may lend insight into the neurobiological systems that are disrupted by this disorder, as well as provide a link between neurobiology and observed symptoms and behaviors. This information can also inform our understanding of the course of the illness and potentially define endophenotypes for further parsing of BD (Glahn et al. 2005
; Christensen et al. 2006
; Antila et al. 2007
; Trivedi et al. 2008
The study of cognitive and neuropsychological functioning in adults with BD suggests that the disorder is associated primarily with impairments in executive function, verbal learning and memory, and attention (Bearden et al. 2001
; Murphy and Sahakian 2001
; Seidman et al. 2002
). Two recent meta-analyses comparing those with BD to healthy controls have found large effects for executive measures such as Category Fluency, Reverse Digit Span, Trail Making Test B, and Wisconsin Card Sorting Test perseverative errors, as well as verbal learning measures such as the California Verbal Learning Test (CVLT) (Robinson et al. 2006
; Arts et al. 2007
). Medium effect sizes were found for deficits on sustained attention tasks. Verbal fluency has been noted as an area of difficulty and shows small-to-medium effect sizes. Measures of general cognitive ability or full-scale intelligence quotient (FSIQ), such as tests of reading or vocabulary, demonstrate the smallest effect sizes.
It is important to understand whether the impairments suggested by these meta-analyses are similar across the life-span or whether they may differ for children and adolescents. Congruence between youth and adult neurocognitive findings would reinforce the similarity in phenotypic definition across the life cycle, providing “laboratory findings” that support the validity of the definition of PBD (Robins and Guze 1970
). More nuanced analyses of pediatric neurocognitive data may also help to disentangle whether neurocognitive features represent a diathesis for PBD, versus a progressive change in brain functioning in response to episodes.
Fewer studies have examined neurocognitive deficits in pediatric cases than adults with BD. These studies have yielded findings of impairment in executive function, memory, attention, and processing speed, as well as differences in intelligence testing results and academic functioning for youth with PBD (e.g., Dickstein et al. 2004
; Doyle et al. 2005
; McClure et al. 2005a
; Bearden et al. 2007
). In a qualitative review of PBD neuropsychological functioning, Kyte et al. (2006
) suggest that impairments in attention, decision-making, and response inhibition are particularly common. These authors also suggest that there are greater similarities than differences in neuropsychological performance between child, adolescent, and adult BD.
Though there has been progress in understanding neurocognitive functioning in BPD, there are many unanswered questions about the nature of potential deficits. Namely, the exact magnitude of deficits for respective cognitive domains remains unclear, as well as whether the existing data suggest global or more specific cognitive deficits. The present paper offers a quantitative and qualitative review of the current literature related to cognitive performance in PBD. The quantitative review focuses on determining the magnitude of PBD/control differences in neurocognitive domains, including FSIQ and academic measures of reading. The qualitative review component focuses on other areas of interest, including differences between individuals with PBD and other conditions, identifying gaps in the literature, and developing recommendations for methodological reporting in future studies of PBD.