Erowid says:
A concerning number of heavy users of DXM report worrisome problems even months after they stop taking the drug. Lasting problems have also been reported by doctors treating very heavy users of PCP and ketamine. Unfortunately, this important message has been drowned in the controversy around whether NAN [NMDA Antagonist Neurotoxicity, also known as Olney's lesions] is the mechanism for these lasting problems. Frequent "recreational" use of these dissociatives can lead to a number of psychological difficulties; in addition to cognitive disruption and annoyances, frequent users may experience delusions of grandeur (i.e., "I'm some sort of messiah"), 'synchronicity' and delusions of reference (i.e., "I was just thinking about my ex-girlfriend, and the sign I just looked at has her name on it, hence the universe must be trying to tell me to go to her house right now"), symptoms similar to manic depression, and a host of other problems.
(Whether one interprets synchronicities and deep insights as "delusions" or "Truth" is, ultimately, a matter of faith not one of logic or evidence, and I'm certainly not going to take a final position on epistemological imponderables. The yardstick for sanity is simply functionality: if you find yourself standing in the middle of the street naked, yelling about the coming apocalypse, the police are not likely to look upon the matter kindly, even [or especially] if you really are a "prophet" of God.)
In addition, regular use of NMDA-dissociatives can complicate academic and professional work and pose serious difficulties for relationships with family, significant others, and friends. Suffice it to say that regular use of these drugs puts a severe strain on one's social interactions. It is hard to be friends with an alien anthropologist, let alone wake up next to one every morning.
NAN is one of several possible explanations for the medium and long term negative consequences of heavy dissociative use. It may be that none of the proposed mechanisms are the cause of the problems reported. The evidence in favor of NAN as the mechanism is equivocal and it is important not to jump to conclusions and foreclose a complete inquiry into the issue.
All of this has been a very long way of saying we still don't know, and users need to be careful whether or not these chemicals cause Olney's Lesions.
If you are using or considering using DXM or other dissociatives, it's your nervous system that you may or may not be "frying". Evaluate your use carefully, and try to be honest. Frivolous use of these drugs seems far from wise; that their use is wise at all is open to considerable question. Many people report life-changing reorientations in philosophical perspective (myself among them); many others report becoming unexpectedly "whacked out", left wondering how they got that way. Try to take care of yourselves, whether on the path of knowledge or in the pursuit of pleasure.
I was getting very rapidly to 0,25mg of clonazepam daily and was at that amount about 1 or 2 weeks without problems but now when I'm without DXM I again find myself strugling with 0,5mg and it doesn't feel enough. So maybe I have to start using DXM again - it was really a powerful stuff for this purpose when used enough.
