When/how acute was the onset?

I’m currently recovering after ~9 months of unexplained, acute-onset brain fog. Some days it was so bad I was mentally unable to drive, or do basic work. I intermittently lost the sensation of physical pleasure. I too, was afraid I’d be ever stupider and die of early-onset alzheimers or something. On my worst day, I was gripped by the horrid fear I was about to lose the ability to communicate and would be infirm, brain-stupefied, in a weird locked-in way the rest of my life. Thankfully, I’ve started getting better for reasons still not understood - I’m not 100% recovered, but I’m like 90% there.

Anyway, the causes are numerous, many people here have laid some out. I suspect in my case that I had otherwise symptomless COVID, but I don’t know. Blood tests are important - various hormone levels, Testosterone levels, long-term infections (eg lyme disease), various vitamin deficiencies, conditions like anemia (pernicious or otherwise) can all cause brain fog and are all detectable with a few blood samples. Things to watch out for - Forms of sleep apnea, intolerances to certain foods, overstress or depression can have a significant input, drug dependence. These are the biggun’s, but as I learned over months, brain fog is a nebulous and poorly understood symptom.

I’m not saying don’t try supplements, but be extremely wary of the promises they and their reviews make. I tried like 10 various supplements out of desperation, and none of them did a damned thing - the placebo effect might’ve helped though, so who knows. As others have said, multivitamins are probably a good just-in-case. In my case, I also did high-dose B12 (>1000mcg), but again, I don’t think it did anything really. Getting sunshine first thing when you wake up, and getting out for a short walk every day will help, even if only a little.

While it’s a total cliche, I’d definitely say that over stressing about it makes it worse. Take it one day at a time, accept this is how you are right now and that you’re slowly, gently, trying stuff to see the best way to recover. I promise you that brain fog IS a reversible symptom in the vast majority of cases, but I 100% know how core-shatteringly scary it is.

You have all my sympathies, feel free to DM if you want to chat to someone who’s been / is going through something similar.