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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptNIH Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
Biol Psychiatry. Author manuscript; available in PMC Sep 8, 2010.
Published in final edited form as:
PMCID: PMC2935847

Effects of Intravenous Ketamine on Explicit and Implicit Measures of Suicidality in Treatment-Resistant Depression



Intravenous ketamine has shown rapid antidepressant effects in early trials, making it a potentially attractive candidate for depressed patients at imminent risk of suicide. The Implicit Association Test (IAT), a performance-based measure of association between two concepts, may have utility in suicide assessment.


Twenty-six patients with treatment-resistant depression were assessed for suicidality 2 hours prior to, and 24 hours following, a single subanesthetic dose of intravenous ketamine using the suicidality item of the Montgomery-Asberg Depression Rating Scale (MADRS-SI). Ten patients also completed IATs assessing implicit suicidal associations at comparable time points. In a second study, 9 patients received thrice-weekly ketamine infusions over a 12-day period.


24-hours after a single infusion, MADRS-SI scores were reduced by an average of 2.08 points on a 0–6 scale (p<.001; d=1.37), and 81% of patients received a rating of 0 or 1 post-infusion. Implicit associations between self- and escape-related words were also reduced following ketamine (p=.003; d=1.36), with reductions correlated across implicit and explicit measures. MADRS-SI reductions were sustained for 12 days by repeated-dose ketamine (2.9-point mean reduction; p<.001; d=2.42).


These preliminary findings support the premise that ketamine has rapid beneficial effects on suicidal cognition and warrants further study.

Keywords: ketamine, suicide, implicit association test
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