ptsd post 2

Who is at risk for developing PTSD?

Janet Ryan-Newell, M.Ed.


As stated in the first post in this series, approximately 9% of individuals will develop post-traumatic stress disorder (PTSD) at least once in their lives (CPA, 2010). Yet, far more than ~9% of adults experience at least one traumatic event during their lifetimes. In fact, Ozer & Weiss (2004) estimate that at least 50% of adults experience significant trauma over the course of their lives, so why do only a small subset of this population suffer from PTSD? This question is central to current PTSD research.

Risk Factors

Can anyone develop PTSD after experiencing trauma? The short answer is yes, but as with most mental (and physical) health disorders, risk factors may significantly increase an individual’s risk of onset. The research into the biology of PTSD is incomplete; however, we do know that an individual’s genes play a role in the development of PTSD. For example, identical and fraternal twin pairs exposed to combat during the Vietnam War have been compared to each other. True et al. (1993) found that having an identical twin with PTSD was highly associated with the co-twin also developing PTSD whereas no such strong association was found between fraternal (non-identical) twins. This research positively implicates individual genetics as an important risk factor since identical twins share ~100% of their genes whereas fraternal twins share only ~50%. There is also some evidence that people born with a congenitally smaller hippocampus (a brain region dealing principally with memory) are also more likely to develop PTSD following trauma.

From an environmental perspective, the National Institute of Mental Health (NIMH; 2016) include the following list of risk factors:

  • living through dangerous events and traumas
  • getting hurt, or seeing another person hurt, or seeing a dead body
  • childhood trauma and adverse life events (ACEs)
  • feeling horror, helplessness, or extreme fear
  • having little or no social support after the event
  • dealing with extra stressors after the event, for example chronic pain or injury
  • experiencing the loss of a loved one, or loss of a job or home
  • having a pre-existing history of mental health issues or substance misuse

Resilience Factors

Likewise, the NIMH (2016) also contrast the list of risk factors with a list of resilience factors which tend to negatively correlate with the development of PTSD (i.e. if you experience any of the following factors, you are less likely – on average – to develop PTSD following trauma):

  • seeking out support from other people, such as friends and family
  • connecting with a support group following a traumatic event
  • learning to feel good about one’s own actions in the face of danger
  • having positive coping strategies for moving through bad events and learning from them
  • being able to act and respond effectively despite feeling fear

Crucially, one’s life history may strongly predict someone’s vulnerability to PTSD, but it does not imply certain causality. Any number of factors could be at play and it is often impossible to isolate a single distinct cause for a particular disorder. Conversely, if you can understand the importance of implementing strategies that build resilience, you can assist someone following a traumatic experience. Supporting a trauma survivor is a vital step along his or her path to recovery. Anyone can develop PTSD following trauma; however, biological and environmental risk factors have been shown to modulate these risks. Similarly, resilience factors have also been studied and found to reduce an individual’s risk of onset; as such, it is often critical to focus on these areas during the recovery phase.


  1. Canadian Psychological Association (CPA). (2010). Canadian Psychological Association > Simple Facts about Traumatic Stress and PTSD. Retrieved from
  2. Ozer, E., & Weiss, D. (2004). Who Develops Posttraumatic Stress Disorder?. Current Directions In Psychological Science, 13(4), 169-172. doi: 10.1111/j.0963-7214.2004.00300.x
  3. National Institute of Mental Health (NIMH). (2016). NIMH » Post-Traumatic Stress Disorder. Retrieved from PTSD/index.shtml#part_145372
  4. True, W. (1993). A Twin Study of Genetic and Environmental Contributions to Liability for Posttraumatic Stress Symptoms. Archives Of General Psychiatry, 50(4), 257. doi: 10.1001/archpsyc.1993.01820160019002