Fresh out of Uni, I thought I'd be a good boy and work harder for my employer at a desk job. After about six months of high stress and little sleep or rest, I'd poisoned my brain with cortisol and needed about 2 years of rehab to be able to read a page of text again.
My cortisol system is still out of whack, probably permanently, sometimes not activating when it should - meaning I can't start tasks or focus or crunch, and activating randomly at other times giving me generalised anxiety for a couple of days at varying intensity.
I'm lucky though, another friend with the same condition lost their ability to walk for a couple of years.
The diagnosis was Exhaustion disorder, cortisol poisoning with a shriveled hippocampus is just one of the physiological symptoms.
My diagnosis was made by psychiatric, GP/somatic, pain sensitivity and blood testing.