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Special Feature Series: Trauma Informed Care – Prevalence of trauma

Trauma prevalence is difficult to establish when looking at the common categories of trauma:

  • Simple or single incident trauma
  • Complex or repetitive trauma
  • Developmental trauma
  • Historical trauma

Research on the epidemiology of trauma (post traumatic stress disorder – PTSD) has focused on three interrelated concepts:

  1. Prevalence of exposure to potentially traumatic events,
  2. Total prevalence of PTSD in the population, and
  3. Conditional risk, which is the prevalence of PTSD given exposure.

In recent years, research on the prevalence of PTSD around the world has increased dramatically and more reliable measures have evolved. However, how a study defines trauma and PTSD, and the assessments that it uses, will strongly affect the results. In addition, the evolving definitions in the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM) have significantly influenced epidemiological findings. (1)

Trauma – Evolving Definitions

For many years, researchers and clinicians alike were pointing to the fact that definitions of trauma were inadequate.

In 2004, Bessel van der Kolk, one of the leading psychiatrists in the trauma field, warned, “Children and adults exposed to chronic interpersonal trauma consistently demonstrate psychological disturbances that are not captured in the post traumatic stress disorder (PTSD) diagnosis”. (2)

In May 2013, the new DSM-V was launched and Psychology Today ran an article by Julian Ford summarizing the new symptom domains with respect to the definition of complex trauma. He humorously entitled the article “PTSD Becomes (More) Complex in the DSM-5: Heading in the right direction, but still not as Complex as the Brain.” (3)

Developmental trauma (The ACE study)

Perhaps the most ground-breaking and astounding trauma prevalence research began in California in the 1990’s, looking at developmental or childhood trauma. Researchers at the University of California conducting weight loss programs noticed that high drop-out rates among participants decreased when participants received emotional support during the program. Researchers began to ask what age people were when they first started putting on weight and what their life circumstances were at that time.

These findings led to a collaboration between the Nation’s leading prevention agency, the Centers for Disease Control and Prevention (CDC), and the Kaiser Health Plan’s Department of Preventive Medicine in San Diego, CA. The objective was to conduct a large scale epidemiological study looking at the general population and correlating adverse childhood events (ACEs) with both acute and chronic health issues later in life. The objective was public health cost savings.

Dr. Anda, the co-principal investigator, described the study:

The key concept underlying the study is that stressful or traumatic childhood experiences such as abuse, neglect, witnessing domestic violence, or growing up with alcohol or other substance abuse, mental illness, parental discord, or crime in the home (which we termed adverse childhood experiences, or ACEs) are a common pathway to social, emotional, and cognitive impairments that lead to increased risk of unhealthy behaviors, risk of violence or re-victimization, disease, disability and premature mortality.” (4)

In the next installment of this feature series, we will take a closer look at the ACE study.


  1. F. Norris, L. Stone. 2013. PTSD Research Quarterly, Vol24/No. 2-3. ISSN:1050-1835.
  2. Bessel A. van der Kolk, Susan Roth, David Pelcovitz, Susanne Sunday and Joseph Spinazzola. 2005. Disorders of Extreme Stress: The Empirical Foundation of a Complex Adaptation to Trauma. Journal of Traumatic Stress, Vol. 18, No. 5, October 2005, pp. 389-399.
  3. http://www.psychologytoday.com/blog/hijacked-your-brain/201306/ptsd-becomes-more-complex-in-the-dsm-5-part-ii Published on June 16, 2013 by Julian Ford, Ph.D. in Hijacked by Your Brain.
  4. Anda, R. 2008. The Health and Social Impact of Growing Up With Adverse Childhood Experiences: The Human and Economic Costs of the Status Quo. Downloaded from http://www.acestudy.org/files/Review_of_ACE_Study_with_references_summary_table_2_.pdf on December 19, 2008.