Increased Intrasubject Variability in Response Time in Youths With Bipolar Disorder and At-Risk Family Members

ObjectiveDeficits in sustained attention may represent an endophenotype for bipolar disorder (BD). One heritable measure of sustained attention is intrasubject variability in response time (ISV-RT). We tested the hypothesis that, compared with controls, both youths with BD and those at familial risk for the disorder would have increased ISV-RT.MethodSubjects were 28 patients with BD, 26 unaffected youths with a first-degree relative with BD, and 24 control youths without an affected relative, all aged 7 to 17 years. Subjects completed the Flanker Continuous Performance Test.ResultsBipolar disorder and at-risk youths had increased ISV-RT, compared with the controls. Differences were independent of comorbid psychopathology in youths with BD and present in psychiatrically healthy at-risk youths.ConclusionsIncreased ISV-RT may be a risk marker for BD. Further research is needed to investigate the neural and genetic underpinnings of this deficit, as well as the specificity of the finding to BD. J. Am. Acad. Child Adolesc. Psychiatry, 2009;48(6):628-635.