Contribution of neurological soft signs’ studies to the understanding of the pathophysiology of schizophrenia

Abstract

Introduction Neurological soft signs (NSS) have long been described in schizophrenic patients. However, recent studies focusing on first-episode psychosis and at-risk mental states have brought up some aspects that may point to a neurodevelopmental underpinning of the disease. Objectives We aimed to review the published literature concerning NSS and psychosis and critically analyze it in regard to how it may constitute a body of evidence favouring the neurodevelopmental hypothesis of schizophrenia. Methods We conducted a Pubmed ® research using the following terms “neurological soft signs”, “psychosis”, “psychotic” and “first-episode”. Results The studies that have been carried out found a gradation of NSS scores that had its minimum values in healthy controls, intermediate scores in at-risk mental state individuals, and highest scores in first-episode psychosis. NSS correlate with various brain imaging anomalies, which indicates abnormal neurological function. Its scores also correlate with poorer cognitive performance and more prominent negative symptoms in the short- and long-term. Interestingly, patients who have psychotic episodes associated with cannabis use have lower NSS scores than all the other psychotic-illness diagnostic groups. Conclusions NSS might thus translate a neurological dysfunction that exists previous to the psychotic break and is a measure of one’s vulnerability to psychosis. These results point to the existence of two distinct groups: one that has high NSS scores and therefore a high genetic vulnerability, needing little contribution of environmental factors to manifest a psychotic episode; and another one with low NSS scores, a smaller genetic vulnerability and a greater role played by environmental influences. Disclosure of Interest None Declared