The validity and diagnostic efficiency of the Davidson Trauma Scale in military veterans who have served since September 11th, 2001

The present study examined the psychometric properties and diagnostic efficiency of the Davidson Trauma Scale (DTS), a self-report measure of posttraumatic stress disorder (PTSD) symptoms. Participants included 158 U.S. military veterans who have served since September 11, 2001 (post-9/11). Results support the DTS as a valid self-report measure of PTSD symptoms. The DTS demonstrated good internal consistency, concurrent validity, and convergent and divergent validity. Diagnostic efficiency was excellent when discriminating between veterans with PTSD and veterans with no Axis I diagnosis. However, although satisfactory by conventional standards, efficiency was substantially attenuated when discriminating between PTSD and other Axis I diagnoses. Thus, results illustrate that potency of the DTS as a diagnostic aid was highly dependent on the comparison group used for analyses. Results are discussed in terms of applications to clinical practice and research.     

Early prognostic screening for posttraumatic stress disorder with the Davidson Trauma Scale and the SPAN

Background: This study examined the accuracy of the 17‐item Dutch version of the Davidson Trauma Scale (DTS) and the four‐item SPAN (Startle, Physiological Arousal, Anger and Numbness) to detect survivors at risk for posttraumatic stress disorder (PTSD) within the first 2 weeks after the trauma. Methods: 203 civilian survivors of recent trauma with relatively mild symptoms completed the DTS a mean of 8.7 days after experiencing trauma. SPAN scores were computed from the DTS. At a mean of 64.6 days posttrauma, 160 respondents were assessed for diagnosis of PTSD with the Structured Interview for PTSD. Results: Receiver operating characteristic curves showed that the DTS showed good overall screening accuracy (84%). At a cut‐off value of 64, the DTS demonstrated a sensitivity of 0.86, a specificity of 0.70, a positive predictive value (PPV) of 0.12, and a negative predictive value (NPV) of 0.98. Overall accuracy of the SPAN was good (89%). At a cut‐off of 10 the SPAN showed a sensitivity of 0.86, a specificity of 0.86, a PPV of 0.22, and a NPV of 0.98. The low PPVs were possibly due to the low of prevalence of PTSD in our sample (4.4%). Conclusions: This study shows that both the DTS and the SPAN are comparably accurate in screening early trauma survivors at risk for developing PTSD. The very brief four‐item SPAN may be preferred over the longer 17‐item DTS especially in settings in which time and resources are limited. Future studies should aim to cross‐validate these results in random samples. Depression and Anxiety, 2008. © 2008 Wiley‐Liss, Inc.     

中国汶川地震现场救援军人创伤后应激障碍及相关因素的调查

目的 调查抗震救灾一线救援军人任务完成6个月创伤后应激障碍(PTSD)的患病率及相关因素.方法 采用目前美国PTSD流行病学调查和诊断工具,按整群分层抽样原则对1125名汶川抗震救灾现场救援军人PTSD的患病率及相关因素进行调查.PTSD诊断采用Davidson创伤量表(DTS)症状发生频率和严重程度总分≥40分标准确定,并使用美国精神障碍诊断与统计手册第4版(DSM-Ⅳ)诊断标准复查,使用SPSS13.0软件对调查资料和DTS诊断结果进行单因素和Logistic回归分析.结果 实际调查1056人;DTS诊断PTSD 69例,患病率6.53%;DSM-Ⅳ复查符合诊断63例,患病率5.97%;独生子女、服役满意度低、吸烟、创伤暴露阶段未进行心理干预及有饮酒习惯者PTSD患病率显著高于相对应的人群(P＜0.05);地震经历暴露程度高(P＜0.01,OR=6.258)、创伤暴露阶段未进行心理干预(P=0.019,OR=3.106)是抗震救灾现场救援军人PTSD的显著危险因素,而独生子女是PTSD潜在的危险因素(P=0.057,OR=2.235).结论 PTSD是抗震救灾现场军人常见的心理障碍,加强创伤暴露者的心理防护和危机干预十分必要.     

The Chinese version of the Davidson Trauma Scale: a practice test for validation

The Chinese version of the Davidson Trauma Scale (DTS-C) was developed to respond to the need of Chinese-speaking individuals. The DTS is a validated self-rating scale used in the diagnosis of posttraumatic stress disorder (PTSD). The DTS-C is translated from DTS through a two-stage translation. Subjects were drawn from a sample of 210 survivors of the 21 September 1999, Chi-Chi Earthquake. The scale showed good internal consistency (Cronbach's alpha = 0.97) and test-retest reliability (r = 0.88). Concurrent validity was obtained against the clinical diagnostic interview, with a diagnostic accuracy of 0.85 at DTS-C score of 44. It showed that the sensitivity was 0.9, specificity 0.81, positive likelihood ratio 4.74, and negative likelihood ratio 0.12. The recommended stratum-specific likelihood ratios were 0.10 (95% CI: 0.05-0.20) for the score range 0-39, 4 (2.22-7.23) for the score range of 40-59, and 6.14 (3.42-11.02) for the scores above 60. In PTSD diagnosed subjects, the factor structures closely resembled the DSM-IV grouping of PTSD symptoms. The psychometric strength of DTS-C is reliable for its future use, particularly for screening for subjects with possible diagnosis of PTSD.     

Posttraumatic stress disorder and body mass index in military veterans. Preliminary findings

Introduction: Current management of posttraumatic stress disorder (PTSD) focuses on the psychiatric parameters of this condition. Little has been written about co-morbid overweight and obesity in PTSD. Methods: We used the database of the recently constituted PTSD program at the Hunter Holmes McGuire Veterans Affairs Medical Center in Richmond, Virginia to assess and better understand the prevalence and severity of overweight and obesity among military veterans with PTSD. Variables assessed included age, decade of life, height, weight, sex, race, and severity and chronicity of PTSD. We used PTSD CheckList-Military Version (PCL-M) to assess current complaints and service-connected disability (SCD) to estimate the long-term severity of PTSD. Results: Of the 221 male veterans extracted from our PTSD database for purposes of this study, 144 (65.2%) were in the age range of 50 to 59 years consistent with Vietnam veterans dominating our study population. Their mean body mass index (BMI) was 30.2+/-5.8 kg/m(2) placing the typical veteran in the obese range. Far exceeding the current US population rate of 64.5%, 82.8% of our study population was either overweight or obese. Our sample had BMI measurements greater than those reported for non-PTSD veterans and also BMI measurements reported in the literature for veterans with PTSD. Current (PCL-M) and long-term (SCD) markers of PTSD did not relate to obesity. Conclusions: The prevalence of overweight and obesity among our veterans with PTSD far exceeded current US population findings and those of other veteran groups with and without PTSD. PTSD symptoms, whether assessed acutely or chronically, did not explain our findings. Prospective studies of PTSD and comorbidity are needed using larger study populations to better understand the relationships among PTSD, stress, and obesity.     

Derivation of the SPAN, a brief diagnostic screening test for post-traumatic stress disorder

The Davidson Trauma Scale (DTS) is a validated 17-item self-rating scale used in the diagnosis of post-traumatic stress disorder (PTSD), which is sensitive to the effects of treatment. It was felt that a shorter version of the scale might provide a better diagnostic screening tool. Subjects were drawn from a sample of 243 patients obtained from multiple cohorts that included a group of survivors of various forms of trauma, including natural disaster, rape and combat. All subjects had diagnostic assessments for PTSD with a clinical interview and completed the DTS. The data were randomly divided between two subsamples, and frequency and severity scores were calculated for the DTS. A four-item scale, the SPAN (named for its top four items: Startle, Physiological arousal, Anger, and Numbness), was developed. It demonstrated an efficiency of 0.88, sensitivity of 0.84, specificity of 0.91 and positive likelihood ratio of 9.1. In a replication sample, values were slightly lower but still acceptable (efficiency = 0.80). A subgroup of PTSD patients received either fluoxetine or placebo in a clinical trial, and a significant SPAN score improvement was observed on fluoxetine. The SPAN, which correlated significantly with the Impact of Events Scale, the Sheehan Disability Scale, and the Structured Interview of PTSD, was found to have a diagnostic accuracy of 88%.     

Advances and Controversies in Military Posttraumatic Stress Disorder Screening

As the longest war in American history draws to a close, an unprecedented number of service members and veterans are seeking care for health challenges related to transitioning home and to civilian life. Congressionally mandated screening for mental health concerns in the Department of Defense (DoD), as well as screening efforts Veterans Affairs (VA) facilities, has been established with the goal of decreasing stigma and ensuring service members and veterans with depression and posttraumatic stress disorder (PTSD) receive needed treatment. Both the DoD and VA have also developed integrated behavioral health in primary-care based initiatives, which emphasize PTSD screening, treatment, and care coordination. This article discusses the rationale for population-level deployment-related mental health screening, recent changes to screening frequency, commonly used screening instruments such as the primary care PTSD screen (PC-PTSD), PTSD checklist (PCL), and Davidson Trauma Scale (DTS); as well as the strengths/limitations of each, and recommended cut-off scores based on expected PTSD prevalence.     

The validation study and application of stratum-specific likelihood ratios in the Chinese version of SPAN

The Davidson Trauma Scale (DTS) is a validated self-rating scale used in the diagnosis of post-traumatic stress disorder (PTSD). A shorter version of the DTS was developed to serve as a diagnostic screening tool. A four-item scale, the SPAN (named for its principal four items: Startle, Physiological arousal, Anger, and Numbness), was then developed. This report investigates the psychometric validation of the Chinese version of the SPAN (SPAN-C). Subjects were drawn from a sample of 210 survivors of the September 21, 1999 Chi-Chi Earthquake. The scale showed good internal consistency (Cronbach's alpha= 0.77) and test-retest reliability (r = 0.90). Concurrent validity was obtained against the clinical diagnostic interview, with a diagnostic accuracy of 0.8 at a SPAN-C score of 5. The recommended stratum-specific likelihood ratios were 0.04 (95% confidence interval [CI], 0.02 to 0.07) for the score range of 0 to 2, 0.93 (95% CI, 0.51 to 1.71) for the score range of 3 to 4, 2.31 (95% CI, 1.17 to 4.57) for the score range of 5 to 6, and 5.23 (95% CI, 3.12 to 8.78) for scores above 7. The psychometric strength of the SPAN-C indicates its reliability for future use, particularly for screening for subjects with a possible diagnosis of PTSD.     

Combined PTSD and depressive symptoms interact with post-deployment social support to predict suicidal ideation in Operation Enduring Freedom and Operation Iraqi Freedom veterans

Rates of suicide are alarmingly high in military and veteran samples. Suicide rates are particularly elevated among those with post-traumatic stress disorder (PTSD) and depression, which share overlapping symptoms and frequently co-occur. Identifying and confirming factors that reduce, suicide risk among veterans with PTSD and depression is imperative. The proposed study evaluated, whether post-deployment social support moderated the influence of PTSD–depression symptoms on, suicidal ideation among Veterans returning from Iraq and Afghanistan using state of the art clinical, diagnostic interviews and self-report measures. Operations Enduring and Iraqi Freedom (OEF/OIF) Veterans (n=145) were invited to, participate in a study evaluating returning Veterans? experiences. As predicted, PTSD–depression, symptoms had almost no effect on suicidal ideation (SI) when post-deployment social support was high; however, when, post-deployment social support was low, PTSD–depression symptoms were positively associated with, SI. Thus, social support may be an important factor for clinicians to assess in the context of PTSD and, depressive symptoms. Future research is needed to prospectively examine the inter-relationship, between PTSD/depression and social support on suicidal risk, as well as whether interventions to, improve social support result in decreased suicidality.     

The Norwegian version of the PTSD Checklist (PCL): Construct validity in a community sample of 2004 tsunami survivors

Background: The PTSD Checklist (PCL) is a widely used self-administered measure of post-traumatic stress disorder (PTSD) and it has been validated in a variety of languages and cultures. Aim: Evaluate the diagnostic validity of the Norwegian version of a specific PCL (PCL-S) for detecting PTSD in epidemiological research. Methods: Participants were severely exposed Norwegian survivors from the 2004 South-East Asian tsunami. Of 75 individuals asked to participate, 63 responded (84%). PTSD was assessed by PCL-S and the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I). These instruments were compared to evaluate the diagnostic validity of the PCL. We used two different scoring methods to diagnose PTSD based on PCL. The first method was based on the dichotomized sum score (cut-off ≥ 50) and the second was based on the flowchart method following DSM-IV symptom criteria. Area under the curve (AUC), Cohen's kappa, sensitivity and specificity were used to evaluate the agreement between the PCL and SCID-I. Results: According to the clinical interview, 11.3% of the participants met the diagnostic criteria for PTSD. The two scoring methods of PCL-S revealed similar results: according to both methods, 14.5% were categorized with PTSD. AUC was 0.98 (95% CI 0.93-1.00). For Cohen's kappa, the agreement was 0.71. Sensitivity was 0.86 and specificity 0.95. Agreement between PCL and SCID-I investigated for each of the three symptom clusters of PTSD and for the 17 individual items showed mostly a moderate to substantial agreement. Conclusions: The Norwegian version of the PCL-S performed well as a diagnostic instrument for detecting PTSD in epidemiological research.     

Combat-related PTSD and psychosocial adjustment problems among substance abusing veterans

The purpose of this study were the following: a) to determine the prevalence of combat-related posttraumatic stress disorder (PTSD) symptoms among veterans seeking assistance at a Veterans Administration medical center substance abuse treatment facility, b) to examine the relative contribution of Vietnam war zone variables to PTSD symptom development, and c) to study psychosocial adjustment problems associated with Vietnam combat exposure and with PTSD symptoms among help-seeking substance abusing men. Of 489 male veterans presenting for treatment, 10.7% had significant Vietnam combat-related PTSD symptoms as measured by the Mississippi Scale for Combat-Related PTSD. Clinically significant PTSD symptoms occurred among 46% of the subsample of combat-exposed Vietnam veterans with substance abuse problems. Degree of combat exposure was the most important military stressor that distinguished Vietnam veterans with PTSD from those without PTSD, but the groups also differed on age of war zone duty, duration of war zone duty, and whether they were wounded. Veterans who served in Vietnam did not differ from veterans who had no war zone duty on various parameters of psychosocial adjustment. However, the subgroup of Vietnam veterans with PTSD symptoms reported significantly greater psychosocial adjustment problems than their counterparts who did not have PTSD. The deleterious effects associated with combat-related PTSD appeared to be confined to adjunctive psychiatric difficulties and unemployment and did not increase risk of arrests for antisocial conduct beyond that found for veterans without PTSD. Methodological and clinical implications of these findings are discussed.     

Posttraumatic stress disorder in male military veterans with comorbid overweight and obesity: psychotropic, antihypertensive, and metabolic medications

Posttraumatic stress disorder (PTSD) is an important syndrome among military veterans. Little has been written about comorbid medical conditions of PTSD, particularly overweight and obesity. We focus on psychotropic and non-psychotropic drugs, their interactions, and metabolic issues most relevant to primary care physicians.Method: Data from the recently constituted PTSD program at the Department of Veterans Affairs Medical Center in Richmond, Va., were retrospectively reviewed to assess the prevalence and severity of comorbid overweight and obesity in male veterans with PTSD. Also, our database allowed us to correlate various drugs used to treat hypertension, diabetes mellitus, and dyslipidemia with body mass index (BMI).Results: The mean BMI of 157 veterans with PTSD (DSM-IV criteria) in this sample was in the obese range (30.3 ± 5.6 kg/m2). The number of drugs a given patient was taking for treatment of hypertension, diabetes mellitus, and dyslipidemia correlated with BMI. Psychotropic drugs associated with weight gain did not explain our findings.Conclusions: Overweight and obesity among our male veterans with PTSD strikingly exceeded national findings. The administration of psychotropic drugs associated with weight gain did not explain these findings. The number of medications used to treat hypertension, diabetes mellitus, and dyslipidemia correlated significantly with BMI. Rather than these medications explaining the high prevalence of overweight and obesity in our study population, obesity probably worsened these components of the metabolic syndrome, necessitating more aggressive treatment reflected in the high number of drugs prescribed.     

Posttraumatic stress disorder and associated risk factors in Canadian peacekeeping veterans with health-related disabilities.

OBJECTIVES: This study investigates posttraumatic stress disorder (PTSD) and its associated risk factors in a random, national, Canadian sample of United Nations peacekeeping veterans with service-related disabilities. METHODS: Participants included 1016 male veterans (age < 65 years) who served in the Canadian Forces from 1990 to 1999 and were selected from a larger random sample of 1968 veterans who voluntarily and anonymously completed a general health survey conducted by Veterans Affairs Canada in 1999. Survey instruments included the PTSD Checklist-Military Version (PCL-M), Center for Epidemiological Studies-Depression Scale (CES-D), and questionnaires regarding life events during the past year, current stressors, sociodemographic characteristics, and military history. RESULTS: We found that rates of probable PTSD (PCL-M score > 50) among veterans were 10.92% for veterans deployed once and 14.84% for those deployed more than once. The rates of probable clinical depression (CES-D score > 16) were 30.35% for veterans deployed once and 32.62% for those deployed more than once. We found that, in multivariate analyses, probable PTSD rates and PTSD severity were associated with younger age, single marital status, and deployment frequency. CONCLUSIONS: PTSD is an important health concern in the veteran population. Understanding such risk factors as younger age and unmarried status can help predict morbidity among trauma-exposed veterans.     

Hopelessness and suicidal ideation in Iraq and Afghanistan War Veterans reporting subthreshold and threshold posttraumatic stress disorder

We examined hopelessness and suicidal ideation in association with subthreshold and threshold posttraumatic stress disorder (PTSD) in a sample of Iraq and Afghanistan War Veterans (U.S., N = 275) assessed within a specialty VA postdeployment health clinic. Veterans completed paper-and-pencil questionnaires at intake. The military version of the PTSD Checklist was used to determine PTSD levels (No PTSD; subthreshold PTSD; PTSD), and endorsement of hopelessness or suicidal ideation were used as markers of elevated suicide risk. Veterans were also asked if they received mental health treatment in the prior 6 months. Veterans reporting subthreshold PTSD were 3 times more likely to endorse these markers of elevated suicide risk relative to the Veterans without PTSD. We found no significant differences in likelihood of endorsing hopelessness or suicidal ideation comparing subthreshold and threshold PTSD groups, although the subthreshold PTSD group was less likely to report prior mental health treatment. Clinicians should be attentive to suicide risk in returned Veterans reporting both subthreshold and threshold PTSD.     

Can we solve the mysteries of the National Vietnam Veterans Readjustment Study?

The National Vietnam Veterans Readjustment Study (NVVRS) researchers reported that 30.9% of all men who served in that conflict developed posttraumatic stress disorder (PTSD) even though only about 15% had been assigned to combat units. Scholars, mainly historians, have questioned the accuracy of the PTSD prevalence rate. The purpose of this article is to evaluate the merits of several hypotheses adduced to explain the high apparent PTSD prevalence in the NVVRS. Empirical and conceptual analysis suggests that malingering is unlikely to account for many cases. Also, deployment to Vietnam in the absence of exposure to classic traumatic stressors is likewise unlikely to account for many cases. There are three plausible explanations for the high prevalence rate of PTSD in the NVVRS. First, DSM-III-R PTSD criteria, used in the NVVRS, did not require that symptoms produce impairment. Accordingly, some PTSD-positive cases may actually have been leading productive lives, despite occasional nightmares, or other stress responses. Second, some men assigned to non-combat duty (e.g., medics) may have been exposed to PTSD-inducing stressors. Third, some respondents may have invoked the Vietnam-PTSD narrative to make sense of postwar psychological difficulties having diverse causes unrelated to their military service. These three factors likely contribute to the high PTSD prevalence rate in the NVVRS.     

Posttraumatic stress disorder in victims of the March 11 attacks in Madrid admitted to a hospital emergency room: 6-month follow-up.

PURPOSE: To determine the change in prevalence of posttraumatic stress disorder (PTSD) symptoms in victims of the March 11 attacks and their relatives, 1 and 6 months after the attacks. SUBJECTS AND METHODS: Evaluation of PTSD symptoms using the Davidson Trauma Scale (DTS) and General Health Questionnaire (GHQ) in a sample of 56 patients admitted to an emergency room of a general hospital, and assessment of PTSD symptoms in relatives of the patients. RESULTS: At Month 1, 41.1% of patients (31.3% of males and 54.2% of females) presented with PTSD. At Month 6, this figure was 40.9% (30.4% of males and 52.4% of females). There was a significant improvement in perception of health among females between Month 1 and Month 6. Relatives presented similar DTS scores at baseline and at 6 months. DISCUSSION: We verified that rates of PTSD did not vary substantively between the two evaluations. PTSD symptoms positively correlated with psychological health involvement. This correlation points out that both PTSD symptoms and subjective general health involvement are part of the psychological response to trauma. CONCLUSION: The prevalence of PTSD symptoms was high and remained stable between Month 1 and Month 6, while subjective perception of health improved significantly.     

Project VALOR: design and methods of a longitudinal registry of post-traumatic stress disorder (PTSD) in combat-exposed veterans in the Afghanistan and Iraqi military theaters of operations

Few studies have investigated the natural history of post-traumatic stress disorder (PTSD). Project VALOR (Veterans' After-discharge Longitudinal Registry) was designed as a longitudinal patient registry assessing the course of combat-related PTSD among 1600 male and female Veterans who served in Operation Enduring Freedom (OEF) in Afghanistan or Operation Iraqi Freedom (OIF). Aims of the study include investigating patterns and predictors of progression or remission of PTSD and treatment utilization. The study design was based on recommendations from the Agency for Healthcare Quality and Research for longitudinal disease registries and used a pre-specified theoretical model to select the measurement domains for data collection and interpretation of forthcoming results. The registry will include 1200 male and female Veterans with a recent diagnosis of PTSD in the Department of Veteran Affairs (VA) electronic medical record and a comparison group of 400 Veterans without a medical record-based PTSD diagnosis, to also allow for case-control analyses. Data are collected from administrative databases, electronic medical records, a self-administered questionnaire, and a semi-structured diagnostic telephone interview. Project VALOR is a unique and timely registry study that will evaluate the clinical course of PTSD, psychosocial correlates, and health outcomes in a carefully selected cohort of returning OEF/OIF Veterans.     

Reliability and validity of the Korean version of the Davidson Trauma Scale

The Davidson Trauma Scale (DTS) is a validated, 17-item, brief global assessment scale for posttraumatic stress disorder (PTSD). The purposes of this study were to develop a Korean version of the DTS (DTS-K) while maintaining its basic structure and to evaluate its reliability and validity for the Korean population. Participants of this study included 93 patients with PTSD (PTSD group), 73 patients with nonpsychotic mood or other anxiety disorders (psychiatric control group), and 88 healthy controls (normal control group). Subjects completed psychometric assessments, including the DTS-K and the Korean version of the Clinician-Administered PTSD Scale and the State Trait Anxiety Inventory. The DTS-K showed good internal consistency (Cronbach alpha = .97) and test-retest reliability (r = .93). The DTS-K showed a significantly positive correlation with Clinician-Administered PTSD Scale (r = .94). The highest diagnostic efficiency of DTS-K was at a total score of 47, with sensitivity and specificity of 0.87 and 0.84, respectively. Our findings suggest that the DTS-K is composed of good psychometric properties and is a valid and reliable tool for assessing the frequency and severity of PTSD symptoms regardless of ethnicity.     

Posttraumatic stress symptoms in Navy personnel: prevalence rates among recruits in basic training

Individuals in the military are often required to endure high levels of stress as a result of demanding operational requirements or deployments. Individuals who enter the military with pre-existing mental health problems such as posttraumatic stress disorder (PTSD) are likely to be at heightened risk of adverse reactions to military stressors. The present study documents the prevalence of PTSD symptoms among new Navy recruits and compares the prevalence of PTSD symptomology among recruits to prevalence rates that have been reported for comparable civilian populations. Results suggest that 15 percent of new Navy recruits are experiencing measurable symptoms of posttraumatic stress. Prevalence of these symptoms among Navy recruits is comparable to that among civilian adolescent and young adult populations.     

Posttraumatic Stress Disorder Post Iraq and Afghanistan: Prevalence Among Military Subgroups

A large body of research has been produced in recent years investigating posttraumatic stress disorder (PTSD) among military personnel following deployment to Iraq and Afghanistan, resulting in apparent differences in PTSD prevalence. We compare prevalence estimates for current PTSD between military subgroups, providing insight into how groups may be differentially affected by deployment. Systematic literature searches using the terms PTSD, stress disorder, and acute stress, combined with terms relating to military personnel, identified 49 relevant papers. Studies with a sample size of less than 100 and studies based on data for treatment seeking or injured populations were excluded. Studies were categorized according to theatre of deployment (Iraq or Afghanistan), combat and noncombat deployed samples, sex, enlistment type (regular or reserve and [or] National Guard), and service branch (for example, army, navy, and air force). Meta-analysis was used to assess PTSD prevalence across subgroups. There was large variability in PTSD prevalence between studies, but, regardless of heterogeneity, prevalence rates of PTSD were higher among studies of Iraq-deployed personnel (12.9%; 95% CI 11.3% to 14.4%), compared with personnel deployed to Afghanistan (7.1%; 95% CI 4.6% to 9.6%), combat deployed personnel, and personnel serving in the Canadian, US, or UK army or the navy or marines (12.4%; 95% CI 10.9% to 13.4%), compared with the other services (4.9%; 95% CI 1.4% to 8.4%). Contrary to findings from within-study comparisons, we did not find a difference in PTSD prevalence for regular active-duty and reserve or National Guard personnel. Categorizing studies according to deployment location and branch of service identified differences among subgroups that provide further support for factors underlying the development of PTSD.