Social Defeat may play a causal role in schizophrenia

Some ethnic minority groups have higher rates of schizophrenia than the general population. My first thought was that the differences were genetic. Current research has found a strong genetic component to schizophrenia, and given that different ethnic groups may have different rates of high risk genotypes, the genetic variation between groups may be in part responsible for the different rates. However, when these groups (often recent immigrants) were compared with those from the broader population of their own national/ethnic origin, there was no evidence of these groups being more genetically “at-risk.” Additional work found that those who had chosen to migrate were not likely different in the degree to which they were genetically predisposed to schizophrenia. There are separate fronts in the battle to understand mental disorder, with many pushing to further ‘biologize’ psychiatric disorders. One danger of over-biologizing is the removal of consideration of other causal explanations. While it may not be the schizophregenic mother that is responsible for the development of schizophrenia in her child, the social environment in which we live and interact likely plays at least a partial role in the development of serious psychopathology, even one as genetically-influenced as schizophrenia. Research on the epidemiology of schizophrenia has found that risk for the disorder increases among nonwhites as their neighborhood composition becomes more white (Halpern, 1993). The repeated findings that minority members are at greater risk depending on the social environment in which they live means that environment may influence the onset, course, and possible origin of schizophrenia (Luhrmann, 2007). This effect has been explained by the experience of "social defeat," which had been used in animal research to term the effect when one animal becomes physically dominant over another. In rats, social defeat appears to increase dopaminergic activity in the mesolimbic dopamine system pathway, which has been found to be associated with positive symptoms in schizophrenia in humans (Tidey & Miczek, 1996).

Most gene x environment research in psychological research has focused on objectively traumatic events (e.g. combat exposure, child sexual or physical abuse), yet the introduction of more subtle environmental “events,” such as discrimination, provides a new avenue of analysis that should be incorporated in the integrative models of psychopathology.

References

Halpern, D. (1993). Minorities and Mental Health. Social Science and Medicine, 36, 597–607.

Luhrmann, T. M. (2007). Social defeat and the culture of chronicity: Or, why does schizophrenia do so well over there and so badly over here? Culture, Medicine and Psychiatry, 31, 135–172.

Tidey, J., & Miczek, K. (1996). Social defeat stress selectively alters mesocorticolimbic dopamine release: An in vivo microdialysis study. Brain Research, 721, 140-149.