Stress and the City: Impact of Urban Upbringing on the (re)Activity of the Hypothalamus-Pituitary-Adrenal Axis

Objective: Urbanization is a major challenge for the 21st century with a significant impact on health; mental health, in particular, can be negatively affected. The mechanisms linking urban living to psychopathology, however, remain unclear. We tested the hypothesis that urban upbringing may alter the activity of the hypothalamus-pituitary-adrenal (HPA) axis, one of the body's major stress response systems. Methods: In three independent experiments (n = 248 in total), we measured the changes in cortisol, the end-product of the HPA axis, in response to different stress tasks (memory recall with critical social evaluation [Experiment 1] or Socially Evaluated Cold Pressor Test [Experiment 2] and to awakening in participants raised in cities or more rural areas. Results: Urban upbringing was associated with elevated cortisol responses to acute stress (task x time point of measurement x urbanicity interaction: F(2,132) = 3.10 [p = .048] in Experiment 1 and F(2,112) = 3.29 [p = .041] in Experiment 2) but with a blunted cortisol awakening response (time point of measurement x urbanicity interaction: F(1,114) = 4.00, p = .048). The autonomic stress response, as indicated by blood pressure measurements, was not affected by urban upbringing. Moreover, current city living was not associated with any changes in the physiological responses to stress or awakening. Conclusions: Our findings suggest that urban upbringing changes the (re) activity of the HPA axis. Given that changes in HPA axis regulation have been associated with several psychiatric disorders, this may represent a mechanism that contributes to the increased risk for psychopathology in urban populations.