My psychiatrist was mentioning this to me a few months ago. The data he’s seen mirrors the study referenced here. This could be a breakthrough for individuals in the midst of major depressions, which are often very hard to treat, considering how long it can take for other anti-depressants to start to work.
Contrary to the posts in this thread there isn't a body of evidence that suggests Ketamine's anti-depressant effect lasts longer than a week.