Reddit mentions of Shamans Among Us: Schizophrenia, Shamanism and the Evolutionary Origins of Religion

You should read Shamans Among Us: Schizophrenia, Shamanism and the Evolutionary Origins of Religion by Joseph Polimeni. He gets deep into the science of evolution to argue that schizophrenia may not be a true disease since it has some value for the survival of the species.

In my opinion, extreme states of inspiration like hypomania, ecstatic trance, and visions may serve the purpose of giving the individual the ability to transcend tired, worn out modes of thought. The tribe then benefits from an individual capable of suggesting new rituals and traditions to replace the old ways of doing things which can become sub-optimal when the ecosystem changes. In other words, an elasticity of the mind can be enormously useful when faced with challenging circumstances. Therefore nature selects for individuals who sacrifice their rigid rationality for a more fluid understanding of reality.

The fact that psychosis often features visions of an apocalypse or dismemberment followed by a rebirth strongly suggests that psychosis is a natural process of refashioning the mind or the society.