Analysis of the attention deficit in schizophrenia: a study of patients and their relatives in Ireland.

County Roscommon, a rural area in the western part of Ireland, was the site of a family study of schizophrenia. As part of this study, we have assessed several elements of attention, identified by principal components analysis in previous investigations, in a group of subjects with schizophrenia, first-degree relatives of subjects with schizophrenia and age- and education-matched controls. The schizophrenic subjects performed significantly more poorly than the controls; the performance of the relatives fell somewhere between the other two groups. Those relatives with a DSM-III-R diagnosis (most frequently, alcohol abuse or an affective disorder) tended to perform more poorly on some of the attention elements than relatives without a diagnosis; in contrast, control subjects with diagnoses were not distinguishable from other controls. The attention elements appeared to differ in their capacity to differentiate the groups and each seemed to have a distinctive profile. The effects of alcohol abuse were also considered. The results obtained with this cohort may provide clues concerning the pathophysiological basis of schizophrenia and the heterogeneity of its expression.