Suicidal ideation following ketamine prescription in patients with recurrent major depressive disorder: a nation-wide cohort study.

Ketamine has gained attention for its effective treatment for patients with major depressive disorder (MDD) and suicidal ideation; Despite numerous studies presenting the rapid efficacy, long-term benefit in real-world populations remains poorly characterized. This is a retrospective cohort study using TriNetX US Collaborative Network, a platform aggregating electronic health records (EHRs) data from 108 million patients from 62 health care organizations in the US, and the study population includes 514,988 patients with a diagnosis of recurrent MDD who were prescribed relevant treatment in their EHRs. The prescription of ketamine was associated with significantly decreased risk of suicidal ideation compared to the prescription of other common antidepressants: HR = 0.63 (95% CI: 0.53-0.76) at 1 day - 7 days, 0.67 (95% CI: 0.59-0.77) at 1 day - 30 days, 0.69 (95% CI: 0.62-0.77) at 1 day - 90 days, 0.74 (95% CI: 0.67-0.81) at 1 day - 180 days, and 0.78 (95% CI: 0.69-0.83) at 1 day - 270 days. This trend was especially robust among adults over 24 years of age, females, males, and White patients with recurrent MDD. This study provides real-world evidence that ketamine has long-term benefits in mitigating suicidal ideation in patients with recurrent MDD. Future work should focus on optimizing dosage regimens for ketamine, understanding the mechanism, and the difference in various demographic subpopulations.