A single infusion of ketamine may reduce suicidal thoughts in people with treatment-resistant depression within four hours, and the effect can last up to 72 hours. The analysis combined 15 randomized controlled trials with 572 participants, mostly with mood disorders. At four hours after infusion, suicidal ideation scores dropped significantly (standardized mean difference -0.51), and the reduction persisted through 72 hours (standardized mean difference -0.57 to -0.63 at different intervals) but not beyond. Results varied widely across studies, and evidence quality was moderate to low. There were almost no data on whether ketamine prevents actual suicide attempts or self-harm. Further trials are needed to confirm these findings and find ways to sustain the anti-suicidal effect.
Twelve fee-paying patients with treatment-resistant depression (ages 21–70, six women and six men, most reporting suicidality and some reporting self-harm) were interviewed before, during, and months after starting ketamine treatment in a routine clinic. Nearly all experienced mood improvement after initial treatments, ranging from negligible to dramatic, and eight reported reduced suicidality. Improvements were generally transitory; two patients had sustained consistent benefit and two had sustained but limited improvement. Some described hopelessness when treatment stopped working, and three experienced increased suicidal ideation. Side-effects were common and significant for two patients. Treatment cost and lack of longer-term benefit were problematic. Suggestions included closer monitoring and adjunctive therapy.