The increased schizophrenia risks for residents of cities with high levels
of competition and for members of disadvantaged groups (for example migrants
from low- and middle-income countries, people with low IQ, hearing
impairments or a history of abuse) suggest that social factors are important
for aetiology. Dopaminergic dysfunctioning is a key mechanism in
pathogenesis. This editorial is a selective literature review to delineate a
mechanism whereby social factors can disturb dopamine function in the brain.
Experiments with rodents have shown that social defeat leads to dopaminergic
hyperactivity and to behavioural sensitisation, whereby the animal displays
an enhanced behavioural and dopamine response to dopamine agonists.
Neuroreceptor imaging studies have demonstrated the same phenomena in
patients with schizophrenia who had never received antipsychotics. In
humans, the chronic experience of social defeat may lead to sensitisation
(and/or increased baseline activity) of the mesolimbic dopamine system and
thereby increase the risk for schizophrenia