An evolutionary perspective on paranoia

Although paranoia is the most commonly presenting symptom of psychosis, paranoid thoughts occur frequently in the general population and range widely in severity, from mild socio-evaluative concerns to frank delusions about the harmful intentions of others. Furthermore, paranoia commonly appears after a surprisingly diverse range of difficulties including trauma, brain injury, sleep deprivation, drug use, and psychiatric and neurological disorder. Evolutionary accounts of paranoia have been proposed before but have largely focused on paranoia as a misplaced threat response. Although social threat is clearly a key component, the experience of paranoia is markedly more complex than these accounts would lead us to believe: paranoia can involve multiple alterations in the perception of the social environment, the identification of specific but seemingly arbitrary groups as the source of persecution, and extended beliefs about conspiracy and complex coordination between the perceived persecutors. Here, we argue for an evolutionary approach to paranoia that more fully accounts for its complex social phenomenology and considers how it can be understood in light of our evolved social cognition. More specifically, in terms of the ability to form coalitions and coordinate between groups in situations of cooperation and competition.