Genome wide association studies (GWAS) have identified many single nucleotide polymorphisms (SNPs) associated with psychiatric disorders. Such GWAS have revealed correlations between SNPs and psychiatric disorders, but not causal association between SNPs and psychiatric disorders. In addition, it was previously impossible to intentionally edit the genome to reconstruct such SNPs in animal models because of technical limitations. Therefore, it remains unclear whether the identified SNPs associated with psychiatric disorders function in the pathophysiology of psychiatric disorders.
 In 1996, zinc finger nucleases (ZFNs) were developed as the first genome editing technology based on the stimulatory effects of DNA double-stranded breaks on homologous recombination repair. However, ZFNs were not widely used because of the technical difficulty in designing DNA recognition sites corresponding to targeted sequences. In 2010, TAL effector nucleases (TALEN) were developed as an alternate genome editing technology which overcame the problem with ZFNs described above. Although TALEN became widely used for a few years, CRISPR/Cas9, a revolutionary genome editing technology entirely different from ZFNs and TALEN, was developed in 2012. It quickly replaced TALEN and has become the most common genome editing technology. CRISPR/Cas9 will greatly advance studies on psychiatric disorders because it facilitates the production of genetically engineered animals.
 This review first provides a history of the development and basic knowledge of genome editing technologies focusing on CRISPR/Cas9. Next, this review discusses the expected roles for CRISPR/Cas9 in future studies on psychiatric disorders.
 <Author's abstract>