There is a gigantic difference in patient outcome between clinical ketamine use and recreational ketamine use. For a variety of reasons: careful dose control, having an actual doctor involved, etc. But the biggest one is the antidepressant effects of ketamine only really happen when it's administered via IV drip over a course of 45 minutes. The most common use of recreational ketamine is inhaling it, the effects come up too fast and go away too fast for the antidepressive effects to occur.