To your point, I think that what you describe is also a common cause for depression. As Freud said (paraphrasing): most of my patient's aren't mentally ill, they just haven't learned how to live well. There is much to be said for the idea that psychological needs are (mostly) physiological needs like sleep, food, water and exercise. If we extend that to include social needs like love, security, a healthy sex life, stimulating conversation and adventure, we start to approach a notion of transcendence.

In our case, I think sleep apnea is a cause. Tripping was never really happening and relief brought on by ketamine was never more than temporary.

But it is true that ketamine can cure depression, at least for a time. It's effectiveness is not something you merely guess at like most meds, if it's working, it seems to simply get rid of the depression outright.

So... definite potential and definite danger, though I think the trips are likely harmful, rather than being the benefit of it.