After analyzing the CYP2C19 *2, *3, and *17 polymorphisms, they found that MDD patients with the PM phenotype (*2/*2, *2/*3, and *3/*3) had significantly higher escitalopram serum concentrations compared to those with the IM (*1/*2 and *1/*3) and NM (*1/*1) phenotypes. Here, CYP2C19 is linked to major depressive disorder.