Genetic association study between the detected risk variants based upon type II diabetes GWAS and psychotic disorders in the Japanese population

Several epidemiological and genetic studies have suggested that the risk of type II diabetes (T2D) is likely to overlap with the susceptibility to psychotic disorders such as schizophrenia (SCZ) and bipolar disorder (BD). In this study, we aimed to examine the association of single-nucleotide polymorphisms (SNPs) detected in previous T2D genome-wide association studies (GWAS) with SCZ, BD and psychosis (SCZ plus BD). A total of 37 SNPs were selected from the literature. A two-stage analysis was conducted using a first set of screening samples (total N=3037) and a second set of replication samples (N=4950). None of the SNPs showed a significant association to the screening samples after correction for multiple testing. To avoid type II error, we genotyped the top three SNPs in BCL11A, HMG20A and HNF4A showing associations with any of the phenotypes (P uncorrected <0.01) using independent samples to replicate the nominal associations. However, we were unable to find any significant associations based on the screening results (P uncorrected >0.05). Our findings did not support the shared genetic risk between T2D and psychotic disorders in the Japanese population. However, further replication using a larger sample size is required.