CCND2 and mental disorder: In addition, we also explored the target genes of miR-15a-5p through three databases, and finally identified 171 possible downstream target genes including CCND1, CCND2, EZH1, AKT3, KDSR, WNT3A, CASK, CDK6, etc., among which CASK has been found to be related to central nervous system diseases and mental disorders [30].