Deficits in sustained attention in schizophrenia but not in bipolar disorder

The aim of the present study was to investigate sustained attention in remitted patients with bipolar disorder and in patients with schizophrenia, as compared to each other and to healthy controls; a secondary aim was to investigate the correlations of different symptom dimensions with performance on sustained attention in the two patient groups. Participants were 29 (18 men) outpatients with schizophrenia (SZ), 19 (8 men) patients with bipolar disorder I (BP) in remission, and 30 (15 men) healthy controls (HC); all three groups were matched on age, sex ratio, and level of education. Symptom severity (positive symptoms, negative symptoms, and general psychopathology) of patients with SZ were assessed with the Greek version of the Positive and Negative Syndrome Scale (PANSS); residual affective symptoms of patients with BP were assessed with the Young Mania Rating Scale (YMRS) and the Montgomery-Asberg Depression Rating Scale (MADRS). Sustained attention was measured by means of the Penn Continuous Performance Test (PCPT). The three groups differed significantly on the PCPT scores. Patients with SZ performed more poorly than both the BP and HC groups, whereas patients with BP did not differ significantly from HC. Performance on the PCPT did not correlate significantly with scores on the YMRS and MADRS in patients with BP. Also, scores on the PCPT did not correlate significantly with scores on any of the three subscales of the PANSS. Outpatients with schizophrenia presented deficits in sustained attention, whereas patients with bipolar disorder I in remission did not manifest such impairment. These results imply that impaired sustained attention might be a more enduring deficit in schizophrenia than it appears to be in bipolar disorder.