Brain Changes Associated With Long-Term Ketamine Abuse, A Systematic Review
Posted for no reason in particular. 
From the NIH, so it may not be there much longer.
Recently, the abuse of ketamine has soared. Therefore, it is of great importance to study its potential risks. The effects of prolonged ketamine on the brain can be observationally studied in chronic recreational users. We performed a systematic review of studies reporting functional and structural brain changes after repeated ketamine abuse. We searched the following electronic databases: Medline, Embase and PsycINFO We screened 11,438 records and 16 met inclusion criteria, totaling 440 chronic recreational ketamine users (2–9.7 years; mean use 2.4 g/day), 259 drug-free controls and 44 poly-drug controls. Long-term recreational ketamine use was associated with lower gray matter volume and less white matter integrity, lower functional thalamocortical and corticocortical connectivity. The observed differences in both structural and functional neuroanatomy between ketamine users and controls may explain some of its long-term cognitive and psychiatric side effects, such as memory impairment and executive functioning. Given the effect that long-term ketamine exposure may yield, an effort should be made to curb its abuse.
Keywords: ketamine, drug abuse, side effects, gray matter volume, white matter volume, connectivity
https://pmc.ncbi.nlm.nih.gov/articles/PMC8972190/
= new reply since forum marked as read
into an illicit recreational one of choice for the wealthy and connected.
It remains a very safe and useful anesthetic induction drug in both human and veterinary medicine--for which there are few enough available for those with serious cardiac or other dysfunction. I will speak for both when I say that such diversions mean not only more controls/shortages of such drugs but difficulties in using them as they were intended. When I mention the veterinary side, I have to say I have great sympathy for how the misdirection of drugs on the human side has caused many to be difficult to acquire on the veterinary side (xylazine for example) or others to be designated controlled when they were not for very many years (e.g., torbutrol).
Not only does this cause safety issues for both humans and animals when these drugs become less available or are abused, but can leave us with fewer options if it ceases to be produced. We saw that years ago with a drug called thiamylal, an injectable barbiturate used similarly to propofol today for both human and veterinary uses--but when US states sought to take over supplies for lethal injection, death penalty opponents in Europe who produced the drug simply chose to cease making it (can't blame them, but damn...)
So, it only adds to my overwhelming disdain for Musk--as if I need more reasons. 
