This piece was originally published in NPR on January 27, 2024, and aired on All Things Considered. 

By Will Stone

Iain Campbell was gazing out the bus window on his way to work when he first sensed something radical was reshaping how he experienced the world.

The inkling emerged from an altogether ordinary observation: He felt peaceful, maybe even happy as he watched the trees along the road pass by.

“I hadn’t experienced that in a really long time, probably since I was a kid,” says Campbell, who lives in Edinburgh, Scotland.

“I didn’t know what was going on at the time, but I thought this might be what it feels like to be normal.”