Deficits in sustained attention in schizophrenia and affective disorders: stable versus state-dependent markers

The authors compared sustained attention deficits measured by the Continuous Performance Test in patients with various affective disorders and patients with schizophrenia and examined whether Continuous Performance Test deficits in patients with affective disorders improve with remission of affective disorder symptoms.

Patients with schizophrenia (N=41), major depression without psychotic features (N=22), bipolar disorder without psychotic features (N=22), and bipolar disorder with psychotic features (N=46) completed Continuous Performance Test sessions with an undegraded version of the test and a 25% degraded version in which the stimulus images were visually distorted. Subjects were also interviewed with the Chinese version of the Diagnostic Interview for Genetic Studies. All inpatients with schizophrenia (N=41) and bipolar disorder (N=15) were assessed both at admission and discharge. Subjects' Continuous Performance Test scores were standardized in comparison with scores for a community sample of 345 subjects, with adjustment for age, sex, and level of education.

Compared with the general population, all patient groups except the group with nonpsychotic major depression were significantly impaired in their ability to discriminate target stimuli from nontarget stimuli on the Continuous Performance Test. Patients with schizophrenia had the severest impairment, followed by patients with bipolar disorder with psychotic features and those with bipolar disorder without psychotic features. From admission to discharge, Continuous Performance Test deficits in schizophrenia remained unchanged, but inpatients with bipolar disorder showed significant improvement on the degraded Continuous Performance Test. All patients adopted a similar response criterion (the amount of perceptual evidence the person requires to decide that a stimulus is a target) to that in the general population, except that the patients with schizophrenia had a less stringent response criterion during the degraded Continuous Performance Test.

Continuous Performance Test deficits are stable vulnerability indicators for schizophrenia, mediating indicators for bipolar disorder, and state-dependent indicators for major depression.