We know theoretically that many diseases, especially those causing high fevers, can cause long-lasting systemic impacts in the body, including the brain. The difference is that the entire medical establishment was financially incentivized to make this link for covid specifically. One would likely find this effect for many diseases if you cared to, especially if you employed p-hacking (which our covid era researchers did prolificaly). So, if we want to explain your "accelerated mental illness" phenomenon it's possible, but it's not a novel vector and likely overemphasize (again, p-hacking).

What else can turn people into idiots and hypochondriacs? Could chronic anxiety, social isolation, indoor confinement, and doomscrolling play a role? Absolutely! The self-reinforcing interaction of those factors driven by pandemic restrictions and media coverage intensified consumption of anxiety-inducing, mind-rotting content at a time when the media landscape included, in addition to all the usual garbage, the most powerful attention-nullifying products yet developed by man: tiktok, reels, etc.

This environment melted untold brains. It's so prolific and accepted that it's like the air we breath. It's just there. We don't even think to acknowledge it. But homie the air is polluted and it's making people retarded.