A large campaign has sought to destigmatize psychiatric disorders by disseminating the view that they are in fact brain disorders. But when psychiatric disorders are associated with neurobiological correlates, laypeople's attitudes toward patients are harsher, and the prognoses seem poorer. Here, we ask whether these misconceptions could result from the essentialist presumption that brain disorders are innate. To this end, we invited laypeople to reason about psychiatric disorders that are diagnosed by either a brain or a behavioral test that were (...) strictly matched for their informative value. Participants viewed disorders as more likely to be innate and immutable when the diagnosis was supported by a brain test as compared to a behavioral test. These results show for the first time that people spontaneously essentialize psychiatric conditions that are linked to the brain, even when the brain probe offers no additional diagnostic or genetic information. This bias suggests that people consider the biological essence of living things as materially embodied. (shrink)