If BP is causing these cognitive problems, what is the mechanism of action?

I would suspect something more along the lines of the depression, mania, and brain fog all being symptoms of some set of underlying conditions -- inflammation, oxidative stress, nutrient deficiencies, toxicity syndromes, infectious disease, leaky gut, environmental problems, hormones, etc etc.

For me brain fog is worse an hour or two following meals, suggesting that something is amiss in the gut. It's also worse post-exertion (physical or mental), and in the afternoon. Better in the evening. Could be adrenal related.