['Sleep disturbance is a reliable marker for differentiating children with bipolar spectrum disorders from those with attention-deficit/hyperactivity disorder. Sleep-related items were extracted from the Parent General Behavior Inventory (P-GBI) to determine whether these items, as a scale unto themselves, demonstrate adequate psychometrics to be useful as a possible endophenotypic marker for bipolar spectrum disorders.', 'From July 2003 to July 2007, 625 youths and their parents completed semistructured Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime version interviews. Parents also completed the 73-item P-GBI.', 'Participants with bipolar spectrum disorders (DSM-IV criteria) scored significantly higher than all other participants on all 7 of the sleep variables (p < .005). On receiver operating characteristic (ROC) analysis, the sleep subscale did substantially as well at discriminating participants with bipolar spectrum disorders as did either of the 2 built-in GBI scales, depression and hypomanic/biphasic (area under the ROC curve = 0.74 vs. 0.75 and 0.77, respectively).'] Do a Parent General Behavior Inventory subscale to measure sleep disturbance in pediatric bipolar disorder?