Neurological soft signs in schizophrenic patients and their nonpsychotic siblings

(a) To investigate the prevalence of neurological soft signs (NSS) in schizophrenic patients and their nonpsychotic siblings and (b) to examine the clinical correlates of NSS in the schizophrenic group.

Ninety-nine schizophrenic patients, 80 of their nonpsychotic siblings and 59 healthy controls were included in the study. NSS were assessed with the Neurological Evaluation Scale (NES). Psychiatric assessment of the patients was conducted with the Positive and Negative Syndrome Scale (PANSS). Siblings and the control group were evaluated with Schedules for Clinical Assessment in Neuropsychiatry (SCAN) to determine the presence of any past or current psychotic disorder.

Schizophrenic patients had significantly higher scores overall and on each subscale of NES than the sibling and control groups. The sibling group's scores were intermediate between those of the schizophrenic patients and those of the healthy controls. All subscale scores and the total NES scores correlated positively with the negative symptoms subscale scores of PANSS. The general psychopathology subscale scores of PANSS also showed a positive correlation with all subscale scores of NES, except the 'sequencing of complex motor acts' subscale. The total NES scores of the patients as well as their scores for the 'sequencing of complex motor acts' and 'others' subscales were significantly correlated with the respective scores of their own siblings.

These results support the findings of previous studies suggesting that there might be common genetic and/or environmental factors in the pathogenesis of neurological impairment in schizophrenic patients and their siblings. They also indicate that neurological soft signs in schizophrenic patients are associated with prominent negative symptoms.