The goal of this study was to infer the effectiveness of midazolam as a comparator in preserving the blind in ketamine studies for mood disorders through patient-level analyses of efficacy trial outcomes. In this integrative data analysis (k = 9, N = 367 patients with mood disorders), clinical outcomes were compared across four groups: ketamine (midazolam-controlled), ketamine (saline-controlled), midazolam, and saline. Ketamine doses ranged from 0.5 to 0.54 mg/kg and midazolam doses ranged from 0.02 to 0.045 mg/kg. The baseline-to-Day 1 effect size was d = 0.7 (95% CI: 0.4-0.9) for ketamine (midazolam) versus midazolam and d = 1.8 (95% CI: 1.4-2.2) for ketamine (saline) versus saline. The effect of ketamine relative to control was larger in saline-controlled studies than in midazolam-controlled studies (t(276) = 2.32, p = 0.02). This was driven by a comparatively larger effect under midazolam than saline (t(111) = 5.40, p < 0.0001), whereas there was no difference between ketamine (midazolam) versus ketamine (saline) (t(177) = 0.65, p = 0.51). Model-estimated rates of response (with 95% CI) yielded similar results: ketamine (midazolam), 45% (34-56%); ketamine (saline), 46% (34-58%); midazolam, 18% (6-30%); saline, 1% (0-11%). The response rate for ketamine was higher than the control condition for both saline (t(353) = 7.41, p < 0.0001) and midazolam (t(353) = 4.59, p < 0.0001). Studies that used midazolam as a comparator yielded smaller effects of ketamine than those which used saline, which was accounted for by greater improvement following midazolam compared to saline.

Beijing Anding Hospital Capital University of Medical Sciences Beijing China

Department of Biostatistics Yale School of Public Health New Haven CT USA

Department of Psychiatry 1st Faculty of Medicine Charles University Prague Prague Czech Republic

Department of Psychiatry Columbia University Medical Center and New York State Psychiatric Institute New York USA

Department of Psychiatry Icahn School of Medicine at Mount Sinai New York USA

Department of Psychiatry Yale School of Medicine New Haven CT USA

Experimental Therapeutics and Pathophysiology Branch National Institute of Mental Health Bethesda MD USA

Menninger Department of Psychiatry and Behavioral Sciences Baylor College of Medicine Houston USA

Mental Health Care Line Michael E Debakey VA Medical Center Houston USA

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