By Jaimie L. Gradus, DSc, MPH
What is epidemiology?
Epidemiology is the study of the distribution and determinants of disease in a population. Numerous studies have been conducted to assess the prevalence of PTSD across different populations. Below is a brief review of some of the major studies that have assessed the prevalence of PTSD in nationally representative samples as well as in samples of Veterans.
What is prevalence?
Prevalence is the proportion of people in a population that have a given disorder at a given time. It represents the existing cases of a disorder in a population or group. Prevalence estimates can be influenced by many factors including disorder occurrence (if new disorder occurrences increase, prevalence will increase) and the duration of the disorder (the longer people live with a disorder, the higher the prevalence). These estimates can also differ by demographic factors such as age and gender. It is important to qualify prevalence estimates with the time at which they were measured, as prevalence estimates can shift over time. Similarly, when interpreting prevalence estimates, it is important to keep in mind that prevalence is dynamic – it can change over people, places, and time.
Often prevalence is discussed in terms of lifetime prevalence. Other times, statistics will be given on current prevalence of PTSD in a given time frame, usually one year. At the end of this fact sheet you will find descriptions of other terms commonly used in epidemiology.
Prevalence of PTSD in the Community
U.S. National Comorbidity Survey Replication
The National Comorbidity Survey Replication (NCS-R), conducted between February 2001 and April 2003, comprised interviews of a nationally representative sample of 9,282 Americans aged 18 years and older. PTSD was assessed among 5,692 participants, using DSM-IV criteria. The NCS-R estimated the lifetime prevalence of PTSD among adult Americans to be 6.8% (1). Current past year PTSD prevalence was estimated at 3.5% (2).The lifetime prevalence of PTSD among men was 3.6% and among women was 9.7%. The twelve month prevalence was 1.8% among men and 5.2% among women (3).
These findings are very similar to those of the first National Comorbidity Survey. The original survey was conducted in the early 1990s and comprised interviews of a representative national sample of 8,098 Americans aged 15 to 54 years. In this earlier sample, the estimated prevalence of lifetime PTSD was 7.8% in the general population. Women (10.4%) were more than twice as likely as men (5%) to have PTSD at some point in their lives (4).
Prevalence of PTSD in Veterans
National Vietnam Veterans Readjustment Study
The National Vietnam Veterans Readjustment Study (NVVRS) , conducted between November 1986 and February 1988, comprised interviews of 3,016 American Veterans selected to provide a representative sample of those who served in the armed forces during the Vietnam era. The estimated lifetime prevalence of PTSD among these Veterans was 30.9% for men and 26.9% for women. Of Vietnam theater Veterans, 15.2% of males and 8.1% of females were currently diagnosed with PTSD at the time the study was conducted (8).
Gulf War Veterans
Kang and others conducted a study to estimate the prevalence of PTSD in a population-based sample of 11,441 Gulf War Veterans from 1995 to 1997. PTSD was assessed using the PTSD Checklist (PCL;9) rather than interviews, with those scoring 50 or higher considered to have met criteria for PTSD. The prevalence of current PTSD in this sample of Gulf War Veterans was 12.1%. Further, the authors estimated the prevalence of PTSD among the total Gulf War Veteran population to be 10.1% (10).
Operation Enduring Freedom/Operation Iraqi Freedom
In 2008, the RAND Corporation, Center for Military Health Policy Research, published a population-based study that examined the prevalence of PTSD among previously deployed Operation Enduring Freedom and Operation Iraqi Freedom (Afghanistan and Iraq) service members (11). PTSD was assessed using the PCL, as in the Gulf War Veterans study. Among the 1,938 participants, the prevalence of current PTSD was 13.8%.