Objectives This study presents the multifaceted effects of candidate loci identified by genome-wide association studies on parameters such as educational background and the clinical symptoms of Japanese patients with schizophrenia along with detailed psychological measurements. This study aimed to investigate whether gene mutations that affect cognitive dysfunction are (1) related to the onset of schizophrenia and (2) also affect cognitive dysfunction in patients with schizophrenia.

Design Case-control study.

Methods This study evaluated 12 single-nucleotide polymorphisms (SNPs) (rs10189857, rs2175263, rs9398171, rs12670234, rs6466056, rs11156875, rs2018916, rs11663602, rs11885093, rs9404453, rs2473938, and rs4275659) that are common in Japanese individuals and demonstrated a relationship with schizophrenia and educational attainment in a previous genome-wide study. We included 640 Japanese patients (schizophrenia group) and 640 healthy participants (control group). Both groups were investigated for the relationship between the SNPs and educational attainment as well as psychometric evaluations of cognitive function.

Results The 12 SNPs were not identified as genetic risk factors for schizophrenia. However, rs9404453 was associated with a decline in educational achievement, educational performance, Japanese Adult Reading Test (JART100) score, and Wechsler Adult Intelligence Scale-Revised (WAIS-R) (full-scale intelligence quotient [FSIQ]) score in patients with schizophrenia, SNP rs6466056 was associated with a decline in the WAIS-R (FSIQ) score, and SNP rs11663602 was associated with a decline in the JART100 score.

Conclusion The SNPs rs9404453, rs6466056, and rs11663602 may be associated with academic performance or cognitive decline in patients with schizophrenia, although the overall findings from psychological tests did not show the expected consistency.