> All of the dissociative drugs likely have this effect, and likely by a common mechanism. Single-dose ketamine can have similar results.

I am only aware of 5 dissociatives: Dextromethorphan, Nitrous oxide, Ketamine, Phencyclidine, and Dimethyltryptamine. I have no idea if all or any of them would be effective at treating depression other than Dextromethorphan and Ketamine. Only Dextromethorphan is readily and legally available without a prescription. While Ketamine has promising results, between the time depression stikes and the date of a Ketamine clinic appointment, sudden death can occur. I'm certainly not telling anyone what to do, but from personal experience, clinical depression sucks and it kills. When facing a 6 week to 3 month delay in even getting a Ketamine clinic appointment, or just a PMH-NP appointment for a more ordinary antidepressent, it is infinitely easier and more comfortable to accept furtive looks at any of the local drug stores and know that by the following morning depression will be gone.

> Unlike with ongoing low-dose dissociatives (which are more likely acting like a classic antidepressant), I suspect the strong single-dose effect is from cognitive changes that occur during the dissociative episode.

I'm not sure cognition exists while asleep, nor if sleeping through a dose can be considered a dissociative "episode." But I do know that dextromethorphan at the doses I mentioned has an irresistible sedative effect, and falling asleep is inevitable, short of taking stimulants.

> It's oddly easy to look (metaphorically or literally) at things that would normally make you flinch (metaphorically or literally). As I once heard it put, you can only die so many times during the trip before you stop worrying about it.

That is clever, but tripping is recreational and neither it nor consciousness is necessary to curing depression with dextromethorphan.

> I am still inclined to a slightly more cautious tone than your post; for example DXM dosing is very sensitive to body weight and 900 mg for a large man vs. small woman will be very different.

This is a very good point, and the dosages mentioned can be considered for average weight and for average depressions. Whether heavier individuals and deeper depressions require larger doses, or with lower than average weight that lower doses will still be effective, I really cannot say, but it seams reasonable.

> At high doses it interacts highly unpleasantly, and potentially dangerously, with a number of drugs, including common antidepressants and ADHD medications. It even interacts strongly with grapefruit.

This is a very good point and mixing any dose of DXM with any other SSRI and even St. Johns Wart could cause Serotonin Syndrome, which can be fatal, but is definitely painfully unpleasant. Grapefruit contains compounds known as furanocoumarins which block CYP3A4 enzymes, reducing the body's ability to break down drugs. Drug blood levels may rise, resulting in a risk of heightened side effects. But I think you'd have to consume a lot of grapefruit or its juice for this to become a serious problem. I can't say for sure because its not in my diet. The OTC antacid drug cimetidine has the same mechanism, but because dosages are concentrated in a pill, the effect can be far greater.