From the article: > Their study involved 40 people with major depressive disorder who were scheduled for routine surgery that required the use of general anesthesia. Half were randomized to receive a single dose of saline solution, the placebo, just before the surgery, and the other half a single dose of intravenous ketamine. The act of going under, the researchers theorized, would eliminate the chances of people going on a typical trip. Then they observed the patients for up to three days.
The article does mention small sample sizes, which should be emphasized.
I would suspect that the high is a necessary part of the treatment being effective.
We could likely replicate this format to show that mushrooms are no better than placebo for depression or that MDMA is no better for PTSD than placebo.
Your assumption that "if ketamine helps with depression we should improvements vs placebo" ignores the considerable likelihood that previous effects in research are the result of conscious interactions with the drug which aren't present in this study. "It sounds like ketamine has a pronounced effect/high" - yeah, and maybe that's the meaningful effect on depression, no?
Ketamine found no better than placebo for depression when both were given to people under general anesthesia.