American Journal of Epidemiology Advance Access published online on September 5, 2008
American Journal of Epidemiology, doi:10.1093/aje/kwn264
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Letter to the Editor |
THE AUTHORS REPLY
1 Behavioral Science and Epidemiology Department, Naval Health Research Center, San Diego, CA
2 Science Applications International Corporation, San Diego, CA
(e-mail: Robyn.Highfill{at}med.navy.mil)
We thank Dohrenwend et al. (1), Smith et al. (2), and Hoge (3) for their perspectives on our paper (4). In their letter, Dohrenwend et al. note that our 1.6% incidence rate of posttraumatic stress disorder (PTSD) (4) is "far lower than rates of ‘probable PTSD’ estimated in previous research of troops serving in Iraq and Afghanistan that has relied on symptom screening scales" (1, p. 000) such as the PTSD Checklist (PCL) (5). The resulting inference—that survey scales would have produced substantially higher incidence estimates in our sample—is likely wrong. To illustrate, Smith et al. (6) recently reported PTSD estimates, based on survey results, of 2.8% and 5.7% for deployed Marines without and with combat exposure, respectively. This finding is important because, to our knowledge, it is the only published data on cohorts comparable to ours, meaning that Smith et al. reported PTSD in deployed Marines experiencing varying levels of combat exposure.
In addition, Terhakopian et al. (7) recently demonstrated that the uncalibrated use of the PCL for incidence estimation, as is commonly the case, may lead to large errors. Terhakopian et al. found that applying the sensitivity and specificity of the PCL to a population with a true PTSD prevalence rate of 15% would result in 27% screening positive for PTSD, almost double the true prevalence. Therefore, one might view PCL-based incidence estimates as an upper bound biased by false positives and estimates based on the International Classification of Diseases, Ninth Revision as a lower bound biased by avoidance of treatment. Most critically, no matter whether surveys or diagnoses are used, estimates of the incidence of PTSD in Marines remain in the low single digits.
Dohrenwend et al. (1) also suggest the possibility that our cohorts may be biased by high stigma among Marines selected for combat. However, research (8, 9) indicates that perceptions of stigma are highest among individuals with mental disorders and/or those experiencing relatively higher levels of emotional distress. Dohrenwend et al.’s proposition about high stigma among Marines selected for combat therefore leads to an untenable scenario wherein troops with mental disorders are also the most likely to be sent to combat. We are aware of no data suggesting that this argument is plausible.
Dohrenwend et al. (1) imply that the association between psychiatric problems and early separation from military service is not well documented. We disagree, and we can point to an extensive literature supporting our position (10–12).
In another letter about our article (4), Hoge (3) states that "any analyses of electronic International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) mental disorder 290-319 codes used in the military health care system will lead to grossly erroneous conclusions about incidence and prevalence" (3, p. 000) in part because "military mental health professionals no longer record ICD-9-CM 290-319 diagnostic codes in the majority of their clinical encounters, even as the primary diagnosis" (3, p. 000). We have examined the source given for this statement (13) and believe that the referenced manuscript (Table 5, specifically) contradicts the claim; ICD-9-CM mental disorder 290-319 codes are reported in far greater numbers than V-codes in the referenced manuscript. Interestingly, we also observed that the referenced manuscript used V-codes reflecting marriage and family problems as proxy measures of mental health, a practice likely to produce distorted conclusions. Additionally, data published by the Armed Forces Health Surveillance Center indicate that the use of psychiatric ICD-9-CM mental disorder codes has continued to increase since 2004, directly contradicting Hoge's (3) concern (14).
Hoge (3) also comments that a true healthy warrior effect would need to include comparison of rates among combat deployed and nondeployed persons who had also completed their first 6 months of service. Our data (4) (and Figure 1 in the paper) demonstrated that the healthy warrior effect persists beyond the first 6 months of service and was evident throughout the study period.
ACKNOWLEDGMENTS
This report was supported by the Bureau of Medicine and Surgery, under Work Unit No. 60518. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the US Government. This research has been conducted in compliance with all applicable federal regulations governing the protection of human subjects in research (Protocol NHRC.2005.0003).
Conflict of interest: none declared.
References
- Dohrenwend BP, Sloan DM, Marx BP. Re: "Psychiatric diagnoses in historic and contemporary military cohorts: combat deployment and the healthy warrior effect" [letter]. Am J Epidemiol (2008) 168. (XX):000–000.
- Smith TC, Ryan MA, Smith B, et al. Re: "Psychiatric diagnoses in historic and contemporary military cohorts: combat deployment and the healthy warrior effect" [letter]. Am J Epidemiol (2008) 168. (XX):000–000.
- Hoge CW. Re: "Psychiatric diagnoses in historic and contemporary military cohorts: combat deployment and the healthy warrior effect" [letter]. Am J Epidemiol (2008) 168. (XX):000–000.
- Larson GE, Highfill-McRoy RM, Booth-Kewley S. Psychiatric diagnoses in historic and contemporary military cohorts: combat deployment and the healthy warrior effect. Am J Epidemiol (2008) 167(11):1269-b–1276.
[Abstract/Free Full Text] - Weathers FW, Litz BT, Herman DS, et al. The PTSD checklist (PCL): reliability, validity, and diagnostic utility. Paper presented at the 9th Annual Conference of the International Society for Traumatic Stress Studies (ISTSS), San Antonio, Texas, 1993.
- Smith TC, Ryan MA, Wingard DL, et al. New onset and persistent symptoms of posttraumatic stress disorder self reported after deployment and combat exposures: prospective population based US military cohort study. BMJ (2008) 336(7640):366–371.
[Abstract/Free Full Text] - Terhakopian A, Sinaii N, Engel CC, et al. Estimating population prevalence of posttraumatic stress disorder: an example using the PTSD checklist. J Trauma Stress (2008) 21(3):290–300.[CrossRef][Web of Science][Medline]
- Hoge CW, Castro CA, Messer SC, et al. Combat duty in Iraq and Afghanistan, mental health problems, and barriers to care. N Engl J Med (2004) 351(1):13–22.
[Abstract/Free Full Text] - Pyne JM, Kuc EJ, Schroeder PJ, et al. Relationship between perceived stigma and depression severity. J Nerv Ment Dis (2004) 192(4):278–283.[CrossRef][Web of Science][Medline]
- Larson GE, Booth-Kewley S, Ryan MAK. Predictors of Navy attrition II: a demonstration of potential usefulness for screening. Mil Med (2002) 167(9):770–776.[Web of Science][Medline]
- Cigrang JA, Carbone EG, Lara A. Four-year prospective study of military trainees returned to duty following a mental health evaluation. Mil Med (2003) 168(9):710–714.[Web of Science][Medline]
- Hoge CW, Lesikar SE, Guevara R, et al. Mental disorders among US military personnel in the 1990s: association with high levels of health care utilization and early military attrition. Am J Psychiatry (2002) 159(9):1576–1583.
[Abstract/Free Full Text] - Hoge CW, Auchterlonie JL, Milliken CS. Mental health problems, use of mental health services, and attrition from military service after returning from deployment to Iraq or Afghanistan. JAMA (2006) 295(9):1023–1032.
[Abstract/Free Full Text] - Armed Forces Health Surveillance Center. Ambulatory visits among members of active components, U.S. Armed Forces, 2006. MSMR (2006) 2007(14):12–17. (http://amsa.army.mil/1msmr/2007/v14_n01.pdf#Cover). (Accessed July 15, 2008).
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