Processing Speed in First Episode of Psychosis and First-Degree Relatives: A Candidate Endophenotype of Spectrum Schizophrenia Disorders

Objective: The processing speed (PS) is highly impacted in individuals experiencing their first episode of psychosis (FEP). Conducting family studies can help to determine whether PS can serve as an endophenotype of schizophrenia spectrum disorders (SSDs), offering valuable insights into the prevention and diagnosis of SSDs. Method: A comprehensive cognitive battery, encompassing tests for PS, verbal memory, visual memory, working memory, executive functions, motor dexterity, and attention, was administered to a sample consisting of 133 FEP patients, 146 parents, 98 siblings, and 202 healthy controls (HCs). Univariate analyses (analysis of covariance [ANCOVA]) were conducted to compare the different cognitive domains between groups, utilizing sex, age, and years of education as covariates and Bonferroni corrections. Effect sizes (ESs) were calculated for estimating the magnitude of differences between groups. Results: Group comparisons revealed significant differences in all cognitive domains. PS was the most impaired function in patients. Parents and siblings had intermediate PS performance between FEP patients and HC. Large ES were observed in PS between FEP versus siblings, FEP versus controls, parents versus controls, and parents versus siblings. Conclusions: Despite not meeting all the necessary criteria, the PS observed in FEP patients and their first-degree relatives suggests its potential as a promising endophenotype of SSDs. Key Points Question: Is processing speed (PS) a candidate endophenotype of schizophrenia spectrum disorders (SSDs)? Findings: Although PS meets most of the criteria to be considered as an endophenotype, the findings of the study do not fully support this conclusion. Importance: Identifying cognitive markers, such as PS, can contribute to the recognition of at-risk populations, facilitating prevention, early diagnosis, and the development of personalized treatment and intervention strategies. Next Steps: Further studies are needed to explore the endophenotype criteria that were not fully met in the current research, providing additional insights into the potential role of PS as an endophenotype of SSDs.