Associations between urban upbringing and cortical thickness and gyrification.

Urbanicity has been linked to several psychiatric disorders, especially schizophrenia. Recent studies suggest effects of urban upbringing and stress on brain structure and function. Here, we used surface-based and voxel-based morphometry to study the effects of urban upbringing in different environments on variation in brain structure in a non-clinical sample. We recruited 85 young and healthy individuals from the community and recorded urban vs. rural background in their first 15 years of live. All participants underwent T1-weighted 3T MRI, which were then processed via CAT12 toolbox (in SPM12) to analyse cortical volume, thickness and gyrification. These parameters were correlated with an established measure of cumulative childhood and adolescence exposure to urban environments. We found significant (p < 0.05, FWE-corrected) negative correlations of cortical thickness with higher index of urban upbringing in the left dorsolateral prefrontal cortex, bilateral medial prefrontal cortices, as well as temporal cortices including the left superior temporal and left parahippocampal cortex. In contrast, results for volume and gyrification (incl. left posterior cingulate cortex) did not survive correction for multiple comparisons. We show a strong association of early-life urbanicity with cortical thickness in several areas, which are also impaired in schizophrenia patients. Along with other findings, these results converge on the dorsolateral prefrontal cortex as an area mediating this environmental risk.