Patients who received ketamine showed a statistically significantly greater reduction in suicidal ideation compared to those who received the control intervention (either saline or midazolam).
This greater improvement was seen on both clinician-administered and self-report scales.
Importantly, the improvement occurred rapidly (within 1 day).
At all time points in the study, the effect sizes were moderate to large (Cohen's d=0.5-0.85). The effect size was largest on day 1 (0.7) and day 2 (0.8). What this suggests is that persons receiving placebo had gradual reduction in suicidal ideation too, but persons who received ketamine showed improvement within the first day or two.
After receiving ketamine, about 55% of participants were free of suicidal ideation on day 1 and about 60% on day 7.
Was the reduction in the suicidal ideation part of the reduction in the severity of depression in general? There was a statistically significant correlation between change in severity of depression and improvement in suicidal ideation. But, in addition to this strong correlation, statistically controlling for the change in severity of depression found that ketamine still had a statistically significantly greater benefit for suicidal ideation compared to control interventions.
The difference between ketamine and the comparison group was more modest when midazolam was the comparator rather than normal saline. For example, at day 1, the effect size was 0.9 in comparison with saline versus 0.6 in comparison with midazolam.