COMT and mental disorder: Several GWASs have identified many variants and estimated a heritability of 8.4 for MDD.[3,30] SNP rs6295 was found to be related to an increased risk of MDD through the suppression of 5-HT1A transcription.[31] Moreover, a GWAS meta-analysis provided several lines of evidence that rs4680 in COMT, is a risk variant for MDD.[32] In addition, LDSC analysis has revealed that MDD is genetically correlated with other mental disorders.[33] However, little is known about the genetic correlation between macronutrient intake, vitamin B intake and MDD.