Differential impairment on measures of attention in patients with paranoid and nonparanoid schizophrenia.

The purpose of the present study is to investigate whether patients with different subtypes of schizophrenia are differentially impaired on measures of attention. Forty-eight patients with schizophrenia (19 paranoid and 29 nonparanoid) and 48 healthy controls (matched on chronological age, sex, and years of education) were administered five measures of attention including the Stroop Color-Word Test (SCWT; Stroop, 1935), the Digit Vigilance Test (DVT; Lewis, 1992), the Symbol Digit Modalities Test (SDMT; Smith, 1982), the Backward Digit Span Test (BDST; Wechsler, 1987), and the Color Trails Test (CTT; D'Elia et al., 1996) to assess selective attention, sustained attention, switching attention, and attentional control processing by the latter two tests respectively. Results from the present study showed that patients with schizophrenia performed poorer on the SCWT, the DVT, and the SDMT, relative to their healthy counterparts. Furthermore, patients with different subtypes of schizophrenia also had different degrees of attentional impairment. While patients with paranoid schizophrenia performed worse on the SCWT, those with nonparanoid schizophrenia performed worse on the SDMT. Nevertheless, these findings may suggest that patients with paranoid and nonparanoid schizophrenia may have different profiles with respect to their performances on measures of attention.