Research provides strong evidence of an elevated risk for developing psychotic symptoms and psychotic disorder among various ethnic and other minority groups. Furthermore, ethnicity may modify the risk for autism-spectrum disorder, but the evidence of this is still thin. Misdiagnosis, selective migration and other methodological artefacts are implausible explanations for the findings on psychotic disorder. Instead, we propose that ‘social defeat’, defined as the chronic experience of being excluded from the majority group, may increase the risk for psychotic disorder by sensitizing the mesolimbic dopamine system. Future challenges lie in connecting the underlying biological mechanisms to behavioral expression in socially excluded groups, as well as in bridging the gap with the clinical field and the wider society by stimulating the implementation of strategies that strengthen the position of minority populations.