Attention profile in schizophrenia compared with depression: differential effects of processing speed, selective attention and vigilance

Objective: The aim of the study is to investigate whether subjects with schizophrenia and major depression display attention deficits for different reasons. Method: Subjects with schizophrenia (n = 53), recurrent major depression (n = 50) and normal controls (n = 50) were administered with 11 measures of processing speed, selective attention and vigilance. Indices of basal speed, speeded attention, non-speeded attention and vigilance were computed. Results: Both clinical groups were impaired on all chronometric tests. The schizophrenic subjects were also more impaired on speeded attention compared with basal processing speed. Only the schizophrenics were impaired on the non-speeded measures of selective attention. Compared with the schizophrenics, the depressives showed a decrement in vigilance. Conclusion: Reduced performance on attention tests in major depression is because of a non-specific speed reduction and loss of vigilance consistent with lack of effort. In addition to generally impaired processing speed, the schizophrenic subjects exposed a deficit in selective attention, indicating executive dysfunction.