Growing up in an urban environment is shown to be a risk factor for schizophrenia. It appears that it is the first 15 years of life in urban area rather than urban birth itself is increasing the risk. This association has shown dose-response relationship and it remains when controlled for potential confounders. The causal mechanisms for this remain unclear.Many support the idea that differences social conditions/ stress between urban and rural environments might account for higher observed risk. Social fragmentation is one notion that is supported by evidence. Social stress in urban healthy individuals is shown to generate MORE neural activity in anterior cingulate cortex.
Can urban upbringing be associated with structural brain changes?
German researchers led by Leila Haddad looked in to this possibility. 110 healthy Germans participated in this MRI brain study. Urbanicity was scored ( city, town, village)based on number of inhabitants in their residential area. a cumulative score ( urbanity, exposure years, early life exposure) was also calculated.
Early life urbanicity scores ( until age 15) correlated negatively with grey matter volume in RIGHT Dorsolateral prefrontal cortex. (DLPFC- broadman’s area 9). Among males, grey matter loss was seen in perigenual anterior cingulate cortex (p ACC) as well.
DLPFC is a stress sensitive area.Early environmental adversity like harsh punishment is shown to reduce DLPFC volume in humans. Structural alterations in DLPFC is seen in schizophrenia. Reduced DLPFC volume is associated with poor cognitive function in schizophrenia. Changes in pACC was seen in males only. Excess risk among males born in urban environments has been previously reported.
Limitations:Population size was used to grade urbanity. This is only a proxy measure. There may be variables that are not controlled for that might explain such associations.Components of urban exposure need to be explored and tested in future research.
Conclusion: Urbanicity is associated with structural effects on brain.
Comments: Social stress early in life is known to have detrimental effects on mental well-being. Policies and interventions that aim better social cohesion is necessary and evidence like these are crucial in building the scientific basis.
Summary of the article:
Haddad L, Schäfer A, Streit F, Lederbogen F, Grimm O, Wüst S, Deuschle M, Kirsch P, Tost H, Meyer-Lindenberg A. Schizophr Bull. 2015 Jan;41(1):115-22