For some users, AI is a helpful assistant; for others, a companion. But for a few unlucky people, chatbots powered by the technology have become a gaslighting, delusional menace.

In the case of Allan Brooks, a Canadian small-business owner , OpenAI’s ChatGPT led him down a dark rabbit hole, convincing him he had discovered a new mathematical formula with limitless potential, and that the fate of the world rested on what he did next. Over the course of a conversation that spanned more than a million words and 300 hours, the bot encouraged Brooks to adopt grandiose beliefs, validated his delusions, and led him to believe the technological infrastructure that underpins the world was in imminent danger.

Brooks, who had no previous history of mental illness, spiraled into paranoia for a

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