GWAS for baseline plasma 5-HT concentrations in our MDD patients identified a single-nucleotide polymorphism (SNP) signal across the glutamate-rich 3 (ERICH3) gene (rs696692, P = 9.28E–08; N = 290), which did not reach the genome-wide significant threshold (P ≤ 5.0E–08). The gene discussed is ERICH3; the disease is major depressive disorder.