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  • Writer's pictureSociety of Bioethics and Medicine

Nature vs Nurture: PTSD

Written by Selma Music

Edited by Jacquelyn Tang

Over 50 percent of Americans report experiencing at least one traumatic event in their lives. However, only an estimated seven percent report developing post-traumatic stress disorder (PTSD). This leads to the question, which has been long debated, if nature or nurture has a greater impact on humans. Nature is the belief that our genetics predispose us to certain personality traits and possible diseases. Nurture is the belief that our environmental upbringing influences our future. The dramatic difference in percentages of people who develop PTSD leads to the question: does genetics or the environment play a more significant role in the development of trauma-induced mental illness?

Most scientists support the perspective that genetic-environment interaction determines a person’s identity. Mirjam Sprangers, a professor and researcher at Amsterdam University, discusses the biological functions of genetic variants involved in emotional states. The hypothalamo-pituitary-adrenal (HPA) axis is considered to be the final common pathway for most depressive symptoms. A majority of the environmental and genetic risk factors for depression correlate with increased HPA-axis activity. An overreaction of the HPA-axis to stress may be based on environmental factors such as placental dysfunction, smoking of the pregnant mother, or child abuse. Additionally, research conducted by Rudolf Uher, a psychiatry professor at Dalhousie University finds that S-allele carriers for the 5-HTT gene who were exposed to a high number of traumatic life events show an increased risk for depression.

Even with this evidence, there are some scientists that claim genetics entirely control one’s emotional well-being. Most people experience trauma at least a few times throughout their lifetimes, however, not every individual develops an anxiety or mood disorder. Anja Schmitz, a clinical psychologist, conducted a study in which 74 healthy subjects were invited and investigated according to their 5-HTT and TPH2 genotype, both serotonin transporters, to examine the influence of genes and traumatic life events on neural responses. The S-allele in 5-HTT has been related to stronger neural responses towards emotional stimuli. Traumatic life events were associated with reduced amygdala activation in S-allele carriers versus non-carriers of the 5-HTT gene. The combined effect of the two alleles indicated an increased expression of fear responses (Schmitz).

Although genetics play a vital role in emotional well-being, research still overwhelmingly shows that the interplay between the environments and genetics affects a person’s ability to respond to trauma. Individuals with the s-5-HTTL allele “are not only vulnerable to negative experiences but also derive more benefit from positive events and social support” (Uher and McGuffin). Thus rather than the genotype making one more vulnerable to mental instability, it actually makes the carrier more reactive to the environment.

In the nature perspective, the past is most important. In the nurture perspective, the present is most important. If the fate of humans was solely in the hands of the past, there would be little hope for improvement of mental health, which has been rebuked countless times through successful therapies. Just like nature can impact mental health, so can nurture. While a person may have a genetic predisposition to a disorder or PTSD, it is nurture that causes the condition to develop, and it is nurture that can also lessen its severity or prevent it from happening.

Schiele, Miriam A., et al. “The Applied Implications of Epigenetics in Anxiety, Affective and Stress-Related Disorders - A Review and Synthesis on Psychosocial Stress, Psychotherapy and Prevention.” ​Clinical Psychology Review,​ vol. 77, 4 Feb. 2020, doi:10.1016/j.cpr.2020.101830.

Uher, Rudolf. “Gene-Environment Interactions in Severe Mental Illness.” ​Frontiers in Psychiatry,​ vol. 5, 10 Dec. 2013, doi:10.3389/fpsyt.2014.00048.

Schmitz, Anja, et al. “Functional Gene Polymorphisms in the Serotonin System and Traumatic Life Events Modulate the Neural Basis of Fear Acquisition and Extinction.” ​PLoS ONE,​ vol. 7, no. 9, May 2012, doi:10.1371/journal.pone.0044352.

Uher, R, and P McGuffin. “The Moderation by the Serotonin Transporter Gene of Environmental Adversity in the Aetiology of Mental Illness: Review and Methodological Analysis.” Molecular Psychiatry​, vol. 13, no. 2, 14 Aug. 2007, pp. 131–146., doi:10.1038/

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