Structural brain abnormalities in schizophrenia in adverse environments: Examining the effect of poverty and violence in six Latin American cities
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Date
2021
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Abstract
Background: Social and environmental factors such as poverty or violence modulate the risk and course of schizophrenia. However, how they affect the brain in patients with psychosis remains unclear. Aims: We studied how environmental factors are related to brain structure in patients with schizophrenia and controls in Latin America, where these factors are large and unequally distributed. Method: This is a multicentre study of magnetic resonance imaging in patients with schizophrenia andcontrols fromsixLatinAmerican cities. Total and voxel-level grey matter volumes, and their relationship with neighbourhood characteristics such as average income and homicide rates, were analysed with a general linear model. Results: Atotal of 334 patients with schizophrenia and 262 controls were included. Income was differentially related to total grey matter volume in both groups (P=0.006). Controls showed a positive correlation between total grey matter volume and The risk of developing schizophrenia is modulated, among other factors, by the social and environmental context of where people live. Incidence rates of psychosis are different across countries,1 possibly reflecting variations in the environment. Proposed specific factors explaining this effect have included an urban upbringing,2 poverty3 and the neighbourhood crime rate.4 Where people live has also been related to recovery rates of schizophrenia, in the context of whether it is a low- or high-income country5 or experiencing periods of economic expansion or recession.6 Brain imaging studies have shown that many of these environmental factors are related to brain changes in healthy individuals. For example, young people raised in poverty in high-income countries show reductions in total brain grey matter.7 Exposure to childhood adversity and violence has also been related to differences in hippocampal and amygdala volumes.8 An unresolved question relates to how these environmental factors affect the biology of schizophrenia. Couldbraindifferences typically seen in patients with schizophrenia be accounted for by these environmental factors? How will the neuropathology of schizophrenia interact with brain changes related to the environment? Is there a double-hit situation, where * Joint last authors. 112 income(R=0.14, P=0.02). Surprisingly, this relationship was not present in patients with schizophrenia (R=−0.076, P=0.17). Voxel-level analysis confirmed that this interaction was widespread across the cortex. After adjusting for global brain changes, income was positively related to prefrontal cortex volumes only in controls. Conversely, the hippocampus in patients with schizophrenia, but not in controls, was relatively larger in affluent environments. There was no significant correlation between environmental violence and brain structure.
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Keywords
Grey matter, Magnetic resonance imaging, Poverty, Schizophrenia, Violence