How many "untreated" bipolars are there actually? It's now been admitted some of the drugs actually cause brain atrophy.

The "brain damage" in "untreated" bipolar has never been proved. You would have to get a group of untreated bipolars that never touched any drug, including alcohol.

Maybe it's that you are studying in 40s... there is a terrible diseases that damages your congitive skills that is called "aging" (no way to treat that to the date, although some swear by lecitin, gingo and such to mitigate the damage. And by engaging your brain constantly). Sorry to say, but you peak in your 20s.

And yes, if you didn't study for a while it's difficult in the beginning. Your brain is not used to that type of activity. But you can get into it.