Goodwin et al.1 report a single 25 mg dose of psilocybin has an antidepressant effect short-term in medication-resistant depression. Unanswered questions include drug blood level as a guide to dose, psychedelic effects relationship to antidepressant benefit, and potential suicide risk of psilocybin.
Importance: A single subanesthetic dose of ketamine produces an antidepressant response in patients with major depressive disorder (MDD) within hours, but the mechanism of antidepressant effect is uncertain. Objective: To evaluate whether ketamine dose and brain glutamate and glutamine (Glx) and γ-aminobutyric acid (GABA) level responses to ketamine are related to antidepressant benefit and...