What are the causes of PTSD

PTSD infographic

Post-traumatic stress disorder (PTSD) is not a condition someone is born with. PTSD develops after a person experiences or witnesses a traumatic event. Trauma can range from bullying or threats to sexual assault, accidents, medical trauma, or exposure to extreme human suffering.

Importantly, experiencing trauma alone does not automatically lead to PTSD. Two people can go through the same event, and only one may develop lasting symptoms. This page explains the main causes of PTSD and the factors that increase or reduce vulnerability.

There are two main factors contributing to the possible development of PTSD: environmental stressors and genetic vulnerability [1]. We’ll discuss each of these causes below, as well as the risk factors and protective factors that influence the likelihood of developing PTSD after experiencing a traumatic event. 

This article was written and clinically reviewed by Niels Barends, MSc, psychologist and founder of Barends Psychology Practice. The information is based on current scientific literature and over a decade of clinical experience working with trauma-related disorders.

If you are reading this because you are struggling with trauma symptoms, you are not alone. PTSD is a treatable condition. With the right support, symptoms such as hypervigilance, avoidance, intrusive memories, and emotional numbness can significantly improve.

 

Need support with PTSD symptoms?
Barends Psychology Practice offers PTSD treatment online and in person.

If symptoms feel severe or urgent, please seek professional support promptly. In an emergency, contact local services.

   

Causes of PTSD – Environmental Stressors

Potential causes of PTSD

 

An environmental stressor can be anything a person experiences that is considered stressful. Some environmental stressors have a greater impact on individuals than others. Sometimes, a stressor has a significant impact on Person A but not on Person B. For instance, a difficult childbirth can be traumatic for Mary, while a similar experience may not be traumatic for Jane.

In clinical practice, we often see that individuals who develop PTSD experience not only the traumatic event itself, but also a sense of helplessness during or after the event. The subjective perception of threat, rather than the objective severity alone, plays a crucial role in whether long-term symptoms develop.

There are several reasons why one traumatic experience can result in PTSD in Mary but not in Jane. We’ll discuss these reasons in the chapters below. 
 
Examples of environmental stressors include childbirth [4], working in high-stress environments such as rescue and recovery operations or military service [5], [6], interpersonal violence (e.g., physical assault, sexual assault, or emotional abuse) [7], [8], accidents, natural disasters, life-threatening illnesses or injuries, murder, and extreme human suffering [8]. 
 
 
Some traumatic events, such as accidents, sexual assault, and murder, cause acute stress and other PTSD-related symptoms immediately. In contrast, for other traumatic events, such as emotional abuse, PTSD-related symptoms may only emerge after some time, sometimes years later. In the latter case, the abuse is less obvious, and the damage done to the victim accumulates over time.
 
Often, a single emotionally abusive event does not cause enough symptoms to meet the criteria for PTSD. However, highly traumatic events such as accidents, murder, and sexual assault often trigger numerous PTSD-related symptoms immediately.
 
In other words: environmental stressors contribute to the development of post-traumatic stress disorder and can be seen as one of its causes. However, experiencing or witnessing a traumatic event alone is not enough to develop PTSD. Other factors, such as genetics, risk factors, and protective factors, also influence the likelihood of developing PTSD. We’ll discuss these protective factors and potential causes of PTSD below.
 
 
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Causes of PTSD – Genetics

In addition to environmental stressors, genetic factors contribute to an individual’s vulnerability to developing PTSD, as well as to their likelihood of being exposed to potentially traumatic events [9]. The first finding suggests that certain genes may negatively affect protective factors, making individuals more vulnerable to PTSD. It could also mean that specific genes influence how traumatic events are processed in the brain.
The second finding suggests that certain genes may impair risk assessment or encourage risk-taking behavior. This increases the likelihood of exposure to potentially traumatic events, especially if someone has poor risk-assessment skills or a propensity for engaging in risky activities.
 
Twin studies estimate PTSD heritability to range from 24% to 72% after a traumatic experience. Additionally, women are two to three times more likely to develop PTSD than men [10], [11], [12], [13].
PTSD heritability estimates indicate that 24% to 72% of the variability in PTSD can be attributed to genetic differences among individuals. This does not mean that 24% to 72% of people will develop PTSD after experiencing or witnessing a traumatic event. Instead, it means that genetic differences account for 24% to 72% of the variability in who develops PTSD.

From a clinical perspective, genetic vulnerability often manifests as heightened physiological reactivity. Some individuals show stronger startle responses, prolonged stress activation, or difficulty returning to baseline after stressful experiences. These biological differences do not cause PTSD on their own, but they can increase susceptibility following trauma.

In other words: Genetic factors, alongside environmental stressors, influence an individual’s vulnerability to developing PTSD and their likelihood of encountering traumatic events. Certain genes may weaken protective factors, affect how traumatic experiences are processed, or increase risk-taking behaviors, raising exposure to trauma. Twin studies estimate that 24% to 72% of PTSD variability is due to genetic differences, with women being two to three times more likely to develop PTSD than men. However, this does not mean that the same percentage of people will develop PTSD, but rather that genetics significantly influence who is more susceptible.
 

 

Which Risk Factors Contribute to the Development of PTSD?

Potential causes of PTSD

No single risk factor directly causes PTSD, but certain factors can indirectly increase the likelihood of developing it:

  • Early-life traumatic experiences: The amount and severity of traumatic experiences in childhood increase the risk that future traumatic events may trigger PTSD.
  • Inherited mental health risks: A family history of conditions like depression or anxiety can increase the likelihood of developing PTSD after a traumatic event.
  • Inherited personality traits: Traits such as temperament may influence the risk of developing PTSD in the future.
  • Occupational exposure: Having a job that frequently exposes you to traumatic events, such as military service, increases the risk of PTSD.
  • Lack of a strong support system: A poor support network can heighten the risk of PTSD following a traumatic event. Talking about your feelings and processing the event helps the mind cope. This is particularly crucial for individuals who are or have been bullied; without a good support system, their chances of developing PTSD increase significantly.

 
 

If you recognize these risk factors, it may help to speak with a professional sooner rather than later.

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Causes of PTSD – Protective Factors

Several factors can protect individuals from developing PTSD, including:
  • Effective coping skills [14],
  • Optimal adaptation abilities [14],
  • High levels of preparedness [15],[16], and
  • Strong social support [16],[17].
  Conversely, poor coping skills, low preparedness, and weak social support increase the risk of PTSD. For example:
  • Preparedness in military personnel: Troops well-prepared before deployment perceived threats proportional to combat exposure. In contrast, unprepared troops perceived high levels of threat regardless of actual combat exposure [15].
  • Rescue and recovery workers: Those with prior disaster experience or training are less likely to develop PTSD [5]. However, prolonged exposure to traumatic environments, such as after the World Trade Center attacks or during the Vietnam War, increases the risk of PTSD [5], [6].
  • Law enforcement officers: Officers with less exposure to critical incidents are less likely to develop PTSD [17].
Having positive world assumptions is another protective factor; assumption such as ‘the world is a good place’ help prevent the development of post-traumatic stress disorder after witnessing or experiencing a traumatic event [17].
 
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The Role of Religious and Moral Beliefs

Religious and moral beliefs can also offer protection against PTSD and its symptoms [18]. Higher scores on moral belief indexes are associated with lower PTSD symptom severity. Additionally, strong religious or moral convictions may help veterans better manage distress. Exploring one’s spiritual needs after a traumatic event can provide further protection against PTSD.

 

 

Professional PTSD Treatment

At Barends Psychology Practice, we provide evidence-based PTSD treatment including EMDR and trauma-focused therapy. Sessions are available online and in person. All consultations are confidential and conducted by licensed professionals.

Frequently Asked Questions about the Causes of PTSD

Can PTSD develop years after a traumatic event?

Yes. In some cases, particularly with prolonged emotional abuse or childhood trauma, symptoms may emerge months or even years later. Delayed onset PTSD is well-documented in clinical literature.

Why do some people develop PTSD and others do not?

The development of PTSD depends on multiple factors, including genetic vulnerability, previous trauma exposure, coping skills, social support, and the subjective perception of threat during the event.

Is PTSD caused by genetics or environment?

PTSD results from an interaction between environmental stressors and biological vulnerability. Experiencing trauma is necessary, but genetic and psychological factors influence whether symptoms persist.

Causes of PTSD – Literature

[1] Smoller, J. W. (2016). The genetics of stress-related disorders: PTSD, depression, and anxiety disorders. Neuropsychopharmacology, 41, 297.  
[2] True, W. R., Rice, J., Eisen, S. A., Heath, A. C., Goldberg, J., Lyons, M. J., & Nowak, J. (1993). A twin study of genetic and environmental contributions to liability for posttraumatic stress symptoms. Archives of general psychiatry, 50, 257-264.  
[3] Stein, M. B., Jang, K. L., Taylor, S., Vernon, P. A., & Livesley, W. J. (2002). Genetic and environmental influences on trauma exposure and posttraumatic stress disorder symptoms: a twin study. American Journal of Psychiatry, 159, 1675-1681.  
[4]  Maggioni, C., Margola, D., & Filippi, F. (2006). PTSD, risk factors, and expectations among women having a baby: a two-wave longitudinal study. Journal of Psychosomatic Obstetrics & Gynecology, 27, 81-90.  
[5] Perrin, M. A., DiGrande, L., Wheeler, K., Thorpe, L., Farfel, M., & Brackbill, R. (2007). Differences in PTSD prevalence and associated risk factors among World Trade Center disaster rescue and recovery workers. American Journal of Psychiatry, 164, 1385-1394.
[6] Xue, C., Ge, Y., Tang, B., Liu, Y., Kang, P., Wang, M., & Zhang, L. (2015). A meta-analysis of risk factors for combat-related PTSD among military personnel and veterans. PloS one, 10.
 

Literature part 2

[7] Kilpatrick, D. G., Ruggiero, K. J., Acierno, R., Saunders, B. E., Resnick, H. S., & Best, C. L. (2003). Violence and risk of PTSD, major depression, substance abuse/dependence, and comorbidity: results from the National Survey of Adolescents. Journal of consulting and clinical psychology, 71, 692.
[8] Spinhoven, P., Penninx, B. W., van Hemert, A. M., de Rooij, M., & Elzinga, B. M. (2014). Comorbidity of PTSD in anxiety and depressive disorders: prevalence and shared risk factors. Child abuse & neglect, 38, 1320-1330.
[9] Amstadter, A. B., Nugent, N. R., & Koenen, K. C. (2009). Genetics of PTSD: fear conditioning as a model for future research. Psychiatric annals, 39.
[10] Sartor, C. E., McCutcheon, V. V., Pommer, N. E., Nelson, E. C., Grant, J. D., Duncan, A. E., … & Heath, A. C. (2011). Common genetic and environmental contributions to post-traumatic stress disorder and alcohol dependence in young women. Psychological medicine, 41, 1497-1505.
[11] True, W. R., Rice, J., Eisen, S. A., Heath, A. C., Goldberg, J., Lyons, M. J., & Nowak, J. (1993). A twin study of genetic and environmental contributions to liability for posttraumatic stress symptoms. Archives of general psychiatry, 50, 257-264.
 

Literature part 3

[12] Stein, M. B., Jang, K. L., Taylor, S., Vernon, P. A., & Livesley, W. J. (2002). Genetic and environmental influences on trauma exposure and posttraumatic stress disorder symptoms: a twin study. American Journal of Psychiatry, 159, 1675-1681.
[13] Wolf, E. J., Mitchell, K. S., Koenen, K. C., & Miller, M. W. (2014). Combat exposure severity as a moderator of genetic and environmental liability to post-traumatic stress disorder. Psychological Medicine, 44, 1499-1509.
[14] Agaibi, C. E., & Wilson, J. P. (2005). Trauma, PTSD, and resilience: a review of the literature. Trauma, Violence, & Abuse, 6, 195-216.
[15] Renshaw, K. D. (2011). An integrated model of risk and protective factors for post-deployment PTSD symptoms in OEF/OIF era combat veterans. Journal of Affective Disorders, 128, 321-326.
[16] Kline, A., Ciccone, D. S., Weiner, M., Interian, A., St. Hill, L., Falca-Dodson, M., … & Losonczy, M. (2013). Gender differences in the risk and protective factors associated with PTSD: a prospective study of National Guard troops deployed to Iraq. Psychiatry: interpersonal & biological processes, 76, 256-272.
[17] Yuan, C., Wang, Z., Inslicht, S. S., McCaslin, S. E., Metzler, T. J., Henn-Haase, C., … & Marmar, C. R. (2011). Protective factors for posttraumatic stress disorder symptoms in a prospective study of police officers. Psychiatry research, 188, 45-50.
[18] Hasanović, M., & Pajević, I. (2010). Religious moral beliefs as mental health protective factor of war veterans suffering from PTSD, depressiveness, anxiety, tobacco and alcohol abuse in comorbidity. Psychiatria Danubina, 22, 203-210.