Estimating PTSD prevalence in US veterans: considering combat exposure, PTSD checklist cutpoints, and DSM-5.

Abstract

Despite the outstanding methodology, this study will no doubt generate questions and debate, like most veteran studies, concerning sample representativeness and interpretation in the context of other research related to the Iraq and Afghanistan wars, PCL validity, or diagnostic changes between DSM-IV and DSM-5. Questions concerning representativeness stem from the observation that veterans account for > 9% of US adults (2010 census5) but were identified in less than 4% of households in Wisco and colleagues’ study sampling frame.1 Nevertheless, this remains one of the only national samples with a high response rate, and the demographic weighting using census figures increases the likelihood that results are nationally representative. Homeless veterans account for 30%,6,7 not useful for projecting health care needs. Such a wide range has been particularly notable when comparing UK and US personnel after Iraq or Afghanistan deployments, with prevalences in UK personnel consistently at the lowest end of the spectrum, though some US studies, such as the Millennium Cohort,8 have produced similarly low estimates. Reasons for the striking differences across studies have been extensively debated, to include differences in demographics, exposure to combat, time between deployments, strategies in sampling, case criteria, level of anonymity of questionnaires, proportion of reservists to active members, and even the possibility of cultural differences.6,7 However, one meta-analysis9 largely resolved this debate by showing that there is much greater consistency across studies than first recognized, provided that studies are suitably grouped. Studies involving stratified random sampling of all deployed personnel, including the large proportion in support roles (eg, UK and Millennium Cohort), yielded a weighted PTSD prevalence of 5.5% (95% CI, 5.4–5.6), comparable to nondeployed personnel, whereas the large body of research focused on combat infantry personnel (mostly US studies) yielded a weighted prevalence of 13.2% (95% CI, 12.8–13.7),9 numbers nicely framing Wisco and colleagues’ overall veteran estimate.1 A follow-up study that directly linked UK and US data confirmed that level of combat exposure largely explained UK/US PTSD prevalence differences.10 H an accurate estimate of the prevalence of posttraumatic stress disorder (PTSD) is critically important for projecting health care needs for veterans now and in coming years. However, prevalence studies in US veterans have produced widely varying estimates, due in large part to lack of representative samples of the entire population, including those who deployed to war zones as well as the large proportion with service not involving war zone deployment. The article by Wisco et al1 in this issue of the Journal of Clinical Psychiatry provides the most comprehensive estimate to date of PTSD prevalence in a national veteran sample, as well as other important findings on trauma exposure, risk factors, and comorbidities useful to clinicians, researchers, and health care administrators. The 4.8% current and 8.0% lifetime prevalence of PTSD reported by Wisco et al1 in veterans overall, based on a stringent score (≥ 50) on the PTSD Checklist (PCL), is not dissimilar to the 3.5% 12-month and 6.8% lifetime National Comorbidity Study-Replication estimates in the general population,2,3 although this comparison is limited due to marked demographic and methodological differences. More similar is the 9.1%, 8.2%, and 7.1% current (30-day) PTSD prevalence in veterans aged 21–29, 30–44, and 45–59 years, respectively, reported by Wisco and colleagues, compared with 8.6% in 1 representative sample of Army personnel (both samples obtained in 2011), although this comparison too is limited by the failure to use the PCL or another wellestablished tool in the Army study.4 Consistent with other research, Wisco et al1 found strong associations of PTSD with number of lifetime traumas, combat exposure, and draft enlistment and strong protective effects of social connectedness and other psychosocial factors (measures related to resilience, optimism, gratitude, curiosity, purpose in life, and community integration). Nearly 90% of veterans reported a lifetime traumatic event (mean = 3.4), with 34% reporting combat exposure. Events carrying highest conditional probability of PTSD (≥ 25%) included sexual assault and high combat exposure (“moderate to heavy” or “heavy” in 7% of participants). The study also confirmed the strong comorbidity of PTSD with other psychiatric conditions.