Neurological soft signs in patients with schizophrenia and their unaffected siblings: frequency and correlates in two ethnic and socioeconomic distinct populations

Abstract

Recent studies have suggested that ethnicity and socioeconomic status may have an impact on the frequency and significance of neurological soft signs (NSS). However, this impact has not been adequately assessed. The objectives were to determine the NSS scores in patients with schizophrenia and their unaffected siblings and to examine the clinical and therapeutic correlates of NSS in two ethnic and socioeconomic distinct populations. Two independent replicate studies were carried out: (1) a French Caucasian sample of 69 patients with schizophrenia, 43 of their unaffected siblings and 108 control subjects; (2) a Tunisian sample of 66 patients with schizophrenia, 31 of their unaffected siblings and 60 control subjects. NSS were assessed with a multidimensional scale, previously validated in drug-naïve and treated samples of patients with schizophrenia. Both patient groups were assessed with the positive and negative syndrome scale (PANSS), the clinical global impressions (CGI) and the global assessment of functioning. NSS total scores were significantly higher in patients with schizophrenia comparatively to siblings and to controls in both studies. The two sibling groups had also higher NSS scores than controls. In addition, NSS total scores were correlated to the PANSS negative and disorganization sub-scores, to the CGI-severity of illness and to a low educational level in both studies. These studies provide a confirmation in two distinct samples of the high prevalence of NSS in patients with schizophrenia, and in their biological relatives, independently of their respective ethnic and socioeconomic origins.