In 2013, Tempei and colleagues reviewed the correlation between DNA methylation and BDNF promoter and found that the expression of BDNF in neural cells is tightly regulated by DNA methylation, thus suggesting a potential usefulness of the DNA methylation status of BDNF as a biomarker of psychiatric disorders including schizophrenia (Ikegame et al., 2013). This evidence concerns the gene BDNF and psychiatric disorder.