Yes. As another data point: I got a severe flu a few years ago and felt inexplicably depressed during the illness and a week afterward. Everything in my life w

Yes. As another data point: I got a severe flu a few years ago and felt inexplicably depressed during the illness and a week afterward. Everything in my life was great, so I could tell it was the illness that caused it. It resolved not too long after. It's very plausible that there is a causal link between inflammation and depression or low oxygen and depression. There is at least correlation between low oxygen over time and poor mental health, which we see in population studies of high places (suicide rates higher, for example).