Neurological soft signs in non-psychotic first-degree relatives of patients with schizophrenia: A systematic review and meta-analysis

Neurological soft signs (NSS) have been associated with the neuropsychopathology of schizophrenia, and have been proposed as candidate endophenotypes for this clinical group. However, the prevalence rate of NSS in non-psychotic first-degree relatives is not fully known. The authors systematically and quantitatively reviewed the literature to determine the magnitude of difference between: (1) first-degree non-psychotic relatives of schizophrenia patients and healthy controls, and (2) between schizophrenia patients and their non-psychotic relatives.An article search and meta-analysis was conducted using the Comprehensive Meta-Analysis software package to quantify group differences. Mean effect sizes (standardized group mean differences) and associated confidence intervals along with homogeneity and publication bias tests and statistics were calculated.Search procedures identified 11 independent studies that met the inclusion criteria. Quantification of NSS differences yielded a mean effect size of 0.81 for schizophrenia patients and their non-psychotic relatives and 0.97 for non-psychotic relatives of schizophrenia patients and healthy controls.The current findings show that there are large group differences in NSS prevalence between patients with schizophrenia, non-psychotic relatives, and healthy controls. These results are consistent with the argument that NSS are familial in nature, segregate with the illness and may be valid and useful endophenotypes.