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Increased intrasubject variability in response time in youths with bipolar disorder and at-risk family members.

OBJECTIVE
Deficits 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.


METHOD
Subjects 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.


RESULTS
Bipolar 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.


CONCLUSIONS
Increased 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.