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."

Campbell had lived with bipolar disorder for much of his life. Mental illness runs in his family, and he'd lost loved ones to suicide. Over the years, he tried different treatments, but it had become "increasingly difficult to live with."

What had changed? A few weeks earlier, he'd started a new diet.

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