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    Created in 2008, Phoenix Rising is the largest and oldest forum dedicated to furthering the understanding of, and finding treatments for, complex chronic illnesses such as chronic fatigue syndrome (ME/CFS), fibromyalgia, long COVID, postural orthostatic tachycardia syndrome (POTS), mast cell activation syndrome (MCAS), and allied diseases.

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Why thinking hard makes you tired


The good news is patients don't die the bad news..
No idea if this affect us ME/CFS patients
Their studies, reported in Current Biology on August 11, show that when intense cognitive work is prolonged for several hours, it causes potentially toxic byproducts to build up in the part of the brain known as the prefrontal cortex. This in turn alters your control over decisions, so you shift toward low-cost actions requiring no effort or waiting as cognitive fatigue sets in, the researchers explain.
Critically, they also had higher levels of glutamate in synapses of the brain's prefrontal cortex. Together with earlier evidence, the authors say it supports the notion that glutamate accumulation makes further activation of the prefrontal cortex more costly, such that cognitive control is more difficult after a mentally tough workday.


Senior Member
Interesting. But the question is how to fix it. For me it's not hours or 'intense' cognitive work. A mildly interesting computer problem will crash me after twenty minutes of focus. Same feeling as I would've gotten from 10 hours of focused work when I was 'mild' CFS. Before CFS, that kinda work would tire me out, but in a good way that didn't lead to a crash.

Rufous McKinney

Senior Member
so in us, the toxic accumulations in the brain, start their accumulating in a mere few minutes!

Thats what it feels like here.

What to do?

I feel a tiny bit better, and a shred of optimism maybe some things I am doing are helping if I just keep persevering.....

so cleaning the brain is tied to this sleep cycle and these accumulations seem to accrue.