polytrip said:
You can't simply use Wikipedia as a source, it is full of errors. In this example you also made an error, as Wikipedia doesn't state that ketamine use results in brain damage. It does state that
chronic use
may result in cognitive impairments, but also "suggests that occasional use of ketamine does not lead to prolonged harm and that any damage that might occur may be reversible when ketamine use is stopped". Next to everything causes brain damage if used in too large dosages and/or too often. Also note that temporarily cognitive impairments is not the same thing as actual brain damage. Then it CAN NOT be seen as proven that ketamine causes brain damage. The Wikipedia article also provides a link to
this Erowid article that should be taken into account.