According to the United States Census Bureau, the current population in America is over a staggering 330 million and increasing. The effect of this population can be seen especially in major cities where most of the population concentrates. This increase in population results in more anonymity and an increased subjective feeling of crowdedness which acts on the Arginine- vasopressin pathway (AVP pathway) and the Hypothalamic-pituitary-adrenal axis (HPA axis), increasing social stress and aggression. As a result, one must conduct a cost-benefit analysis before relocating to an urban environment.

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More people living in a specific region can increase the sense of crowdedness. This crowdedness and chronic stressors can activate direct physiological challenges and threaten homeostasis (McEwen et al., 2015). One crucial impact of this disturbance in homeostasis is the constant activation of the HPA axis. The HPA axis is the network of interaction and association between the Hypothalamic-pituitary-adrenal. This network is responsible for releasing cortisol via the adrenal cortex, which is “a valid and reliable biomarker of physiologic stress that can be measured from saliva, urine, hair, blood plasma, and serum” (Jones et al., 2021). It is then without a doubt that measuring cortisol levels in the urban population would show an increased cortisol level, implicating the chronic activation of the HPA axis. In the study by Kann et al. (2015) that examined the alteration of Cortisol Homeostasis in changes in the Sociocultural Environment and metabolic rate within developing countries, they found that Ovahimba people of the urban environment had a significantly higher cortisol exposure than their rural counterparts as well as negative patterns of dietary habits and physical activity. This finding highlights that the transition to urban living does not just impact stress levels with the increased cortisol exposure and alters consumed food and activities.

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Furthermore, the increasing crowding density from the increased population among urban residents increases the “protein expression of AVP” (Huang et al., 2021). Crowding density can be understood as “any experience of spatial limitation that creates inconveniences” (e.g., privacy) (Stokols, 1972). In this sense, the consequent effect of a more populated area, despite the feeling of anonymity, is aggression. This can be seen in the high crime rates in urban areas.

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This is the case because, as presented previously, crowded high density increases the protein expression of AVP, and the “injection of AVP in the MPOA-AH region increase[s] aggressive behaviour” (Hennessey et al., 1994). This sequence only follows that the presentation of crowding density can impact behaviour. Stress stimulates the HPA axis through the paraventricular nucleus (PVN). This stimulation releases corticotropin-releasing hormone (CRH) and AVP (Huang et al., 2021). In this context of crowding, this path of stimulation creates a downward spiral of the overall well-being of residents of urbanicity feeling crowded.

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In conclusion, the presented effects of crowding, which often arise from the increased population density of urbanicity, can be highly detrimental if not compensated for healthily, like maintaining physical activity, spending time in nature, and exposing oneself to calm surrounding. Even though the population increase creates a fog of anonymity, it also increases social stress and aggression with the biological stimulation of the Arginine-vasopressin pathway (AVP pathway) and the Hypothalamic-pituitary-adrenal axis (HPA axis). All this, coupled with the increased crime rates in highly dense environments, is noteworthy. Overall, knowing the impact one’s environment has, in addition to the ability to alter the environment to one’s ability, should be deeply considered before deciding to relocate to a more populated and denser environment.

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Ẹniọlá Adeoye-Lawal, Intern, IASIS NGO

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Citations

  • Huang, S., Li, G., Pan, Y., Song, M., Zhao, J., Wan, X., … & Zhang, Z. (2021). Density‐induced social stress alters oxytocin and vasopressin activities in the brain of a small rodent species. Integrative zoology, 16(2), 149-159.
  • “U.S. and World Population Clock.” United States Census Bureau, https://www.census.gov/popclock/world.
  • Hennessey AC, Huhman KL, Albers HE (1994). Vasopressin and sex-differences in hamster flank marking. Physiology & Behavior 55, 905–11.
  • Jones, R., Tarter, R., & Ross, A. M. (2021). Greenspace interventions, stress and cortisol: a scoping review. International journal of environmental research and public health, 18(6), 2802.
  • Kann, P. H., Münzel, M., Hadji, P., Daniel, H., Flache, S., Nyarango, P., & Wilhelm, A. (2015). Alterations of cortisol homeostasis may link changes of the sociocultural environment to an increased diabetes and metabolic risk in developing countries: a prospective diagnostic study performed in cooperation with the Ovahimba people of the Kunene region/northwestern Namibia. The Journal of Clinical Endocrinology & Metabolism, 100(3), E482-E486.
  • McEwen BS, Bowles NP, Gray JD, Hill MN, Hunter RG, Karatsoreos IN, Nasca C (2015) Mechanisms of stress in the brain. Nat Neurosci 18: 1353–1363
  • Stokols, D. (1972). On the distinction between density and crowding: some implications for future research. Psychological review, 79(3), 275.