Randomization
With the use of stratified block randomization, patients were randomized (1:1) to the PIT or control group by a staff member not involved in this study. The stratification was performed in the following order: (1) CYP2D6 metabolizer phenotype (and CYP2C19 metabolizer phenotype for those receiving imipramine), categorized as poor metabolizer (PM), intermediate metabolizer (IM), normal metabolizer (NM), and ultrarapid metabolizer (UM); (2) prescribed drug (nortriptyline, clomipramine, or imipramine); and (3) clinical setting (inpatient or outpatient), except for patients treated with imipramine who had a deviant metabolizer phenotype (PM, IM, or UM) for both CYP2D6 and CYP2C19 (eTable 3 in In our original design, only patients with aberrant metabolizer phenotypes (PM, IM, or UM) were randomized to the PIT or control group, and patients with a CYP2D6 NM phenotype were assigned to the reference group. This reference group received the same treatment as the control group. After acceptance of a protocol amendment on November 25, 2019, all patients were randomized to the PIT or control group.