The metabolic genophenotypes of the CYP enzymes CYP2D6, CYP2C19, and CYP2C9 can be classified as normal metabolizer (NM), intermediate metabolizer (IM), poor metabolizer (PM), or ultra-rapid metabolizer (UM), and patients with AD who were classified as NMs or IMs responded significantly better to current treatments for depression and anxiety than those who were classified as PMs or UMs [41]. Here, CYP2D6 is linked to major depressive disorder.