Beyond athletic performance and chronic fatigue, some neurologists and psychiatrists have recently suggested that every mental disorder (literally, the entire DSM) has a single underlying cause: mitochondrial dysfunction. If that's true, mitochondria transplants could solve the mental health crisis.
On this topic, Brain Energy by Christopher Palmer: https://www.goodreads.com/book/show/61129785-brain-energy . Very interesting book, highest recommendation.
What I got out of the book was two things:
* Mitochondria are freaking cool.
* The DSM is bollocks and metabolic dysfunction explains all mental illness.
Despite how radical the above sounds, the evidence for it is overwhelming. The book is largely an accessible tour of the evidence. It's well cited without being too academic.
And while Dr. Palmer is a prominent spokesperson for this movement, there are hundreds of other neurologists, psychiatrists and doctors on the same line.