The National Vietnam Veterans Longitudinal Study, Part 1

Dr. Charles Marmar discusses the science and practice of PTSD.

Posted Sep 23, 2015

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The National Vietnam Veterans Readjustment Study (NVVRS) was conducted in 1983 as a response to a congressional mandate for an investigation of PTSD and other postwar psychological problems among Vietnam veterans. More than 25 years after the original NVVRS study was conducted, researchers reassessed more than two thousand of the original study participants for symptoms of PTSD. What made this research unique was that the long-term course of PTSD in military personnel had not previously been evaluated in a nationally representative sample. This follow up study, called the National Vietnam Veterans Longitudinal Study (NVVLS), found a current prevalence of PTSD in 4.5% of male and 6.1% of female combat Vietnam era veterans. Extrapolating these figures suggests that more than a quarter of a million Vietnam veterans still struggle every day with the consequences of PTSD forty years after that war ended. 

The study was led by Charles R. Marmar, MD, the Lucius N. Littauer Professor  and chair of the department of Psychiatry at NYU Langone Medical Center and director of its Steven and Alexandra Cohen Veterans Center, a leading program in the study of PTSD. A pioneer in the field of PTSD research, his work has led to breakthroughs in our understanding of PTSD through the study of police officers, soldiers in combat, veterans, and civilians who have been exposed to sudden, usually life-threatening, events.

Recently, I spoke to Dr. Marmar about the implications of the NVVLS study and about his 40 year career as a PTSD researcher.

Dr. Jain: For my first question, can you start by commenting on the large percentage of Vietnam veterans you and your team studied that has never suffered from PTSD linked to war? I feel sometimes that percentage gets lost in some of the headlines and media coverage of PTSD research.

Dr. Marmar: Yes. It is a little difficult to give a precise overall estimate, but if you look across our data from both the first wave of our study (collected between '84 and '88) and then the second wave (collected between 2011 and 2013), it is roughly a 75% and 25% split.  Of course it depends precisely on how you define PTSD, and that has changed over the years, but you could say that approximately 3/4 of Vietnam veterans who served in the warzone never developed significant levels of stress, anxiety, or depression related to their military service. They were relatively resilient. Now, that is only an average across all 3.1 million men and women who served. There is a lot of variability depending on who you were, how old you were, how many times you were deployed, and what your service duties entailed. In a warzone deployment, there are three broad roles: combat, combat support, and service support. All three roles come under the definition of a warzone, but the number of people who are actually repeatedly at the tip of the sword is a smaller percentage, and that factors in to the individual risk calculation.

Dr. Jain: Yes. Actually as you talk, something comes into my mind about recent returnees from the conflicts in Afghanistan and Iraq.  Military rank appears crucial. Lower ranking military members are exposed to higher doses of trauma and are therefore more vulnerable. Is that something that you looked at in the Vietnam study or is that something you can offer some feedback on?

Dr. Marmar: In general, older, more educated war fighters of higher rank are able to tolerate the intensity of combat and are more resilient. Also, as you indicated, in general, their levels of repeated combat exposure are lower if they were squad leaders rather than squad members.

Dr. Jain: Dr. Hoge’s editorial that accompanied the article described your research as “methodologically superb.” Can you comment a little bit from a researcher's perspective on the strength of your study and how it is different to previous efforts to document the prevalence or course of PTSD in this population?

Dr. Marmar: Firstly, we believe it is the only study in the world (with the possible exception of studies conducted by Solomon et al with the Israeli Defense Force) which followed, in an epidemiologically sound way, a representative sample of every man and every woman who served in a major conflict. The study was not done by recruiting people from VA hospitals and clinics or by advertising on Craigslist, etc. So it takes into account the differences between community samples and VA seeking patients, as these are two very different groups. This study was drawn top down from military records. It included people from all 50 states, Guam, and Puerto Rico, and it included urban, suburban, rural, and extremely remote veterans. So, for example, we have included participants from the remote aspects of the Big Island of Hawaii, all the way to Manhattan. It is a truly representative sample in this regard. Secondly, we oversampled for women and minorities. This gave us more statistical power to look at these populations too. Thirdly, the study is exceptionally successful in its implementation. We had zero contact with our cohort for 25 years. We never contacted a single one of them on a single occasion and still retained just under 80% of them for the follow up 25 years later. The study has many excellent features, but the most important features are that it has true representational sampling, overrepresentation of women and minorities, and its high retention rate over 25 years.

Dr. Jain: That’s what makes it a very important piece of science in our understanding of the prevalence and course of PTSD.

Dr. Marmar: It also tells you something profound about the participants’ commitment to the research. Another thing is it is very deep, because we have up to 5-hour household interviews, survey interviews, and 3-hour clinical interviews on a sub-sample. For this follow up study, we had a 1-hour self-report package, 1 to 2-hour interview by professional survey interviewers, and 3 to 5-hour clinical interviews done by my team at NYU. We used a team of highly qualified PhD clinical interviewers, and they were able to interview people by telephone so that we could sample, in the clinical interview, people from all over the country. It is very hard to do that if you ask participants to come into regional medical centers. 

In my next blog post, I'll share the second half of my interview with Dr. Marmar.

Copyright: Shaili Jain, MD. For more information, please see PLOS Blogs.