Genetic influences of Schizophrenia and Intelligence Independently Associate with General Cognitive Function in Middle-Aged Adults

A hallmark symptom of schizophrenia is cognitive impairment, which is also observed in first-degree relatives of schizophrenia patients. Schizophrenia and cognition have independent genetic loci associated with them. We... [ view full abstract ]

A hallmark symptom of schizophrenia is cognitive impairment, which is also observed in first-degree relatives of schizophrenia patients. Schizophrenia and cognition have independent genetic loci associated with them. We tested whether: i) polygenic scores of risk for schizophrenia predict general cognitive function in an adult male twin sample, and ii) the association is independent of a polygenic score for intelligence. We used a mixed effect linear regression to account for non-independence of twins and zygosity via random effects, and covaried for genome-based ancestry in addition to health and lifestyle influences known to affect cognitive performance via fixed effects. Higher schizophrenia risk scores were associated with lower levels of cognitive function across a variety of assessments which were aggregated via principal components analysis into an index of general cognitive function. We found that the schizophrenia and intelligence polygenic scores were both significantly associated with general cognition. These results suggest that the common variants identified in genome-wide association studies for schizophrenia are associated with lower general cognition and that this effect is independent of common variants previously associated with intelligence.