Effects of Low-Dose Ketamine Infusion on the Positive and Negative Domains of Hopelessness and Suicidal Thoughts

Low-dose ketamine infusion has been demonstrated to exert antisuicidal effects on patients with treatment-resistant depression (TRD) and strong suicidal ideation. Although evidence suggests an association between hopelessness and suicidality, very few studies have investigated the antihopelessness effects of ketamine. , Fifth Edition, diagnostic criteria for major depressive disorder. They were randomly assigned to receive a single infusion of either 0.5 mg/kg ketamine or 0.045 mg/kg midazolam. Hopelessness and suicidal symptoms were assessed at baseline, at 240 minutes postinfusion, and on Days 2, 3, 7, and 14 postinfusion. The assessments were performed using the self-report Beck Hopelessness Scale (BHS) and Positive and Negative Suicide Ideation Inventory (PANSI). The analysis focused on the positive and negative domains of the BHS and PANSI, respectively. The clinical trial was conducted between August 15, 2018, and November 30, 2021. = .031). Notably, the observed ketamine-induced reduction in hopelessness at 240 minutes postinfusion was associated with its antisuicidal effect on Day 2 postinfusion. A single infusion of low-dose ketamine resulted in a brief (∼4 hours) yet significant reduction in hopelessness. Subjective antisuicidal effects of ketamine were noted on Day 2 postinfusion. Further studies are needed to elucidate the neuromechanisms underlying the antihopelessness and antisuicidal effects of ketamine. UMIN Clinical Trials Registry identifiers: UMIN000033916 and UMIN000033760.