[gibba999]

A study in isolation should not be persuasive. There's a pipeline from idea to hypothesis the theory to fact, which includes many studies with many methodologies.

On the other hand, a handful of studies, one correlational with large n, a few causal, a good theoretical basis, etc. do move us up that pipeline quite a bit.

Mild and asymptomatic cases of COVID19 due seem to cause brain damage leading to brain fog.

- Reports of brain fog in isolation? Psychosomatic.

- Correlational studies? Correlation is not causation.

- Case studies? Anecdotal.

- Extrapolation from olfactory symptoms? Theoretical.

And so on.

Put together, though, it's a pretty strong case. It's not airtight, but it's well into the well-supported theory range.

[timr]

> brain damage leading to brain fog.

Define "brain fog". Tell me what the diagnostic criteria are, and how one might make an objective measurement of its presence and magnitude.

Bonus question: tell me how your stated criteria differs from the pre-established diagnostic criteria for depression.

One can survey a random sample of the population, ask them if they have ever "felt the presence of God", and find a strong signal confirming this. It does not make God a diagnostic factor in a medical study.

[cloverich]

> tell me how your stated criteria differs from the pre-established diagnostic criteria for depression.

If the person lacks dysphoria or anhedonia, would that satisfy the question? I understand your angle (I think), but for comparison, the last time I had a serious flu I found that even after I felt better, it was extremely difficult to focus at work. For about 3 days, gradually improving each. I suspect that is what people refer to as "brain fog", and I could distinguish it from depression by (among other things) a lack of dysphoria / anhedonia (and generally speaking, other depression signs).

I remember in medical school that when we were interviewing patients receiving chemo they would have us do a neuro exam, and very distinctly remember when one guy got angry at me when he couldn't answer some of my questions. He didn't seem to have depression and nobody told me I was doing it wrong when I said he had "chemo brain". So its certainly a real thing in the general sense, and can certainly be caused by a variety of medical conditions.

I guess a more constructive question would be -- assuming a long term cognitive impact, what (practical) research should these researchers be doing instead? Or what if when they asked about brain fog they _also_ asked about depressive symptoms?

[timr]

> If the person lacks dysphoria or anhedonia, would that satisfy the question?

No. That is certainly more specific than ~all of what you hear in the media surrounding "brain fog", but you can't define something by what it isn't.

Example: I have the wiggles. I'm not itchy though, and my muscles don't hurt.

OK, great. What are the wiggles?

> the last time I had a serious flu I found that even after I felt better, it was extremely difficult to focus at work. For about 3 days, gradually improving each. I suspect that is what people refer to as "brain fog"

Could be! The problem is, until there's a definition (and ideally some kind of objective measure), all of these self-reports are blind people describing different parts of an elephant.

> I guess a more constructive question would be -- assuming a long term cognitive impact, what (practical) research should these researchers be doing instead? Or what if when they asked about brain fog they _also_ asked about depressive symptoms?

We could start by simply using established terminology and testing. What percentage of patients reporting "brain fog" show up as depressed using a standard screen?

It's literally the easiest thing in the world to do...why isn't it done?