Reaction time measures of sustained attention differentiate bipolar disorder from schizophrenia

Although continuous performance tasks (CPTs) are becoming more common in psychiatric research, it remains unclear which performance measures best differentiate psychiatric patient groups and along which psychological dimensions. To address this the authors examined sustained attention decrements in patients with bipolar disorder and schizophrenia using CPT measures of perceptual sensitivity, response bias, and psychomotor processing speed. Patients with bipolar disorder with psychotic features (N = 20), schizophrenia (N = 20), and healthy controls (N = 20) were evaluated using structured clinical inter-views. These patients were rated with the Scale for the Assessment of Positive Symptoms and the Young Mania Rating Scale before completing a degraded-stimulus version of the CPT. Psychomotor processing speed was the only measure that reliably differentiated the groups across the entire vigilance period and was the strongest predictor of group membership. These findings suggest that reaction time measures may be sensitive to differences in the sustained attention abilities of patients with bipolar disorder and schizophrenia. By incorporating reaction time measures into CPT assessments, discriminant ability may be enhanced. (C) 2001 Elsevier Science B.V. All rights reserved.