rpsych | This article proposes a reformulation of the social brain theory of
schizophrenia. Contrary to those who consider schizophrenia to be an
inherently human condition, we suggest that it is a relatively recent
phenomenon, and that the vulnerability to it remained hidden among our
hunter-gatherer ancestors. Hence, we contend that schizophrenia is the
result of a mismatch between the post-Neolithic human social environment
and the design of the social brain. We review the evidence from human
evolutionary history of the importance of the distinction between
ingroup and out-group membership that lies at the heart of intergroup
conflict, violence, and xenophobia. We then review the evidence for the
disparities in schizophrenia incidence around the world and for the
higher risk of this condition among immigrants and city dwellers. Our
hypothesis explains a range of epidemiological findings on schizophrenia
related to the risk of migration and urbanization, the improved
prognosis in underdeveloped countries, and variations in the prevalence
of the disorder. However, although this hypothesis may identify the
ultimate causation of schizophrenia, it does not specify the proximate
mechanisms that lead to it. We conclude with a number of testable and
refutable predictions for future research.
