Schizophrenia is a complex polygenic neuropsychiatric and brain disorder involving a wide range of cognitive, emotional and social function impairments. Despite the advance in genetics and genomics, genes that confer susceptibility to the disorder have not been definitively identified. One of the main unresolved issues is the lack of an appropriate phenotype for schizophrenia.
MEEHL Paul has posited that there may be specific traits (schizotype) that confer genetic liability and predispose an individual to develop a state of mental and cognitive disorganization named schizotypy, which in turn constitutes a predisposition to schizophrenia. Previous studies have shown that schizotypy can be detected in the general population using reliable and valid self-reported measures. However, it is unclear whether the construct of schizotype is stable across the spectrum of schizophrenia.
To bridge this gap of knowledge, Dr. CHAN Raymond from the Institute of Psychology, Chinese Academy of Sciences and Prof. GOODING Diane from the University of Wisconsin, Madison, have conducted a study to examine the invariance model of schizotypy using a set of measures specifically developed to capture this construct. The invariance model is a stringent statistical method to examine the stability of factors supposedly captured by the measures across three independent samples. In particular, they examined whether patients with schizophrenia would have higher scores on the schizotypy measures than their unaffected first-degree relatives, who in turn, were expected to have higher mean scores than healthy individuals.
They recruited 196 patients with schizophrenia, 197 unaffected first-degree relatives and 1724 healthy individuals. Their findings showed that the best-fitting model was a two-factor model with negative schizotypy and positive schizotypy. These results were consistent across the three samples. For both negative and positive schizotypy traits, patients with schizophrenia reported significantly higher scores than their unaffected first-degree relatives, who in turn reported significantly higher scores than healthy individuals. Based on these results, three types of schizotypes were identified, the clinical schizotype (patients with schizophrenia), the biologically-identified schizotypes (unaffected first-degree relatives) and the psychometrically-identified or behavioural schizotypes (non-clinical individuals). Dr. CHAN and Prof. GOODING commented that schizotype may be an appropriate or “right” phenotype for studying schizophrenia spectrum disorders which may facilitate cross-cultural and/or genetic investigations.
This study was supported by the National Natural Science Foundation of China, the Beijing Training Project for the Leading Talents in Science & Technology, the ’Strategic Priority Research Program (B)’ of the Chinese Academy of Sciences and the CAS/SAFEA International Partnership Program for Creative Research Teams, the Leon Epstein Faculty Fellowship for Research from the University of Wisconsin-Madison, and a donation grant from the Philip K. H. Wong Foundation.