The Social Defeat Hypothesis of Schizophrenia: An Update

Abstract

According to the social defeat (SD) hypothesis, published in 2005, long-term exposure to the experience of SD may lead to sensitization of the mesolimbic dopamine (DA) system and thereby increase the risk for schizophrenia. The hypothesis posits that SD (ie, the negative experience of being excluded from the majority group) is the common denominator of 5 major schizophrenia risk factors: urban upbringing, migration, childhood trauma, low intelligence, and drug abuse. The purpose of this update of the literature since 2005 is to answer 2 questions: (1) What is the evidence that SD explains the association between schizophrenia and these risk factors? (2) What is the evidence that SD leads to sensitization of the mesolimbic DA system? The evidence for SD as the mechanism underlying the increased risk was found to be strongest for migration and childhood trauma, while the evidence for urban upbringing, low intelligence, and drug abuse is suggestive, but insufficient. Some other findings that may support the hypothesis are the association between risk for schizophrenia and African American ethnicity, unemployment, single status, hearing impairment, autism, illiteracy, short stature, Klinefelter syndrome, and, possibly, sexual minority status. While the evidence that SD in humans leads to sensitization of the mesolimbic DA system is not sufficient, due to lack of studies, the evidence for this in animals is strong. The authors argue that the SD hypothesis provides a parsimonious and plausible explanation for a number of epidemiological findings that cannot be explained solely by genetic confounding.

Towards integrating phenomenology and neurocognition: Possible neurocognitive correlates of basic self-disturbance in schizophrenia

“…Such a model of schizophrenia is consistent with the widely accepted findings, from the last decade or two, that demonstrate the role of prolonged stress, trauma, social defeat, and cultural collision in the pathogenesis of schizophrenia (see, e.g., [158,159]). It may help to account as well for a related finding: the extensive overlapping between schizophrenic and dissociative symptoms [160].…”

The mental-health crisis among migrants

“…Jean-Paul Selten, a psychiatrist at Maastricht University in the Netherlands, is also exploring the poisonous nature of social stress. He proposes that pressures such as social exclusion raise the risk of psychosis by changing the brain's sensitivity to the neurotransmitter dopamine 6 . Germany's integration plans, consolidated in a law that came into force in August, involve distributing refugees across the country to avoid the creation of large, isolated ethnic communities.…”

Social defeat predicts paranoid appraisals in people at high risk for psychosis

“…However, the mechanisms by which stress influences the onset of psychosis remain unknown. Previous studies have suggested that lower perceived social rank is associated with paranoid ideation (Atherton et al, in press;Freeman et al, 2014;Gilbert et al, 2005) and it has been proposed that the cumulative effect of prolonged exposure to social adversity and exclusion can lead to a state of 'social defeat', which may confer an increased risk of psychosis (Johnson et al, 2011;Selten, 2013;Selten and Cantor-Graae, 2005;Wicks et al, 2005). The concept of social defeat originates from animal research after it was observed that when an animal is put in a cage with another animal, they fight for dominance.…”