Clinical studies have found that repeated systematically administered high-dose recombinant human EPO versus placebo (saline) improves attention, memory, and executive functions after 8–12 weeks of treatment across neuropsychiatric disorders, including multiple sclerosis, Parkinson’s disease, schizophrenia, treatment-resistant depression (TRD; defined as failure to respond to ≥ 2 different types of antidepressant treatments given in sufficient doses over sufficient time [38]), and BD [39–43]. This evidence concerns the gene EPO and treatment resistant depression.