A 2009 study by Baker et. al. examined PTSD by branch of service. This week we will use data they collected to answer the question: “Is there evidence that there is a difference in the proportion of military veterans diagnosed with PTSD by service branch?”
The study included 339 veterans from four branches: the army, navy, marines, and national guard. Read the paper and use it to answer the following questions. Refer to the section of the paper where the researchers discuss how they recruited their participants as well as the introduction.
***I have attached the paper***
(1a) What is the researchers’ population of interest?
(1b) Did the researchers select participants by random sampling from their entire population of interest? Support your answer by explaining their sampling procedure, and why it does or does not fit the definition of a random sample.
(2a) What kind of study design the the researchers use?
(2b) Did the researchers use random allocation to assign study participants into branch of service? Support your answer by explaining their design procedure, and why it does or does not fit the definition of a random allocation (a.k.a. randomization a.k.a. randomized experiment).
(3) Based on your answers to questions 1 and 2, can the researchers establish a causal claim? Can the researchers generalize their results to the entire population of interest? VOLUME 174 AUGUST 2009 NUMBER 8
MILITARY MEDICINE
ORIGINAL ARTICLES
Authors alone are responsible for opinions expressed in the contribution and for its clearance through their federal health agency, if required.
MILITARY MEDICINE, 174, 8:773, 2009
Trauma Exposure, Branch of Service, and Physical Injury in Relation to Mental Health Among U.S. Veterans
Returning From Iraq and Afghanistan
Dewleen G. Baker, MD*??; Pia Heppner, PhD*??; Niloofar Afari, PhD*??; Sarah Nunnink, PhD*??; Michael Kilmer, MSW?; Alan Simmons, PhD*?; Laura Harder, BA?; Brandon Bosse, MS?
ABSTRACT Signi?cant mental health symptoms are reported in troops deployed to Iraq and Afghanistan (OEF/OIF). Symptomatic troops are more likely to be discharged and become eligible for Department of Veterans Affairs (DVA) care. Prevalence and predictors of mental health symptoms were assessed in 339 OEF/OIF veterans and reservists reg- istering at the San Diego DVA. Participants completed self-report questionnaires assessing combat exposure, post- traumatic stress disorder (PTSD) symptom frequency and severity, depression, and substance and alcohol abuse. A minority of participants (36%) did not screen positive for mental health symptoms; the remainder met threshold for case- ness of PTSD, depression, or substance and alcohol abuse. Using a hierarchical logistic regression model, gender, age, race, and rank were not signi?cantly related to PTSD caseness, whereas most recent branch of service and report of injury during combat were. Follow-up analyses revealed that trauma history and combat exposure varied by branch of service. Knowledge of base rates and vulnerability factors can aid in rapid detection of ?at risk? individuals.
INTRODUCTION
There is extensive literature indicating that deployment to combat zones and exposure to combat are associated with increased risk of mental health problems, such as post- traumatic stress disorder (PTSD), alcohol use disorders, and depression.1?11 The wars in Iraq and Afghanistan are no excep- tion. Several recent studies have reported high rates of mental health symptoms and substantial distress in service members or veterans returning from Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF).3,12?16 Positive men- tal health screens in troops deployed to Iraq are nearly twofold of those obtained before deployment.3
*University of California, San Diego, Department of Psychiatry, 9500 Gilman Dr., MC 0603 La Jolla, CA 92093-0603.
?Veterans Affairs Center of Excellence for Stress and Mental Health, San Diego, 3350 La Jolla Village Dr., MC 116A San Diego, CA 92161.
?VA San Diego Healthcare System, 3350 La Jolla Village Dr., San Diego, CA 92161.
This manuscript was received for review in September 2008. The revised manuscript was accepted for publication in April 2009.
Although the rates of mental health problems vary on the basis of methods of assessment and population (e.g., branch of service or location of deployment), OEF/OIF veterans? self- reported rates of PTSD and/or depressive symptoms range from 10 to 44%13,14 and a quarter of OEF/OIF veterans evalu- ated at U.S. Department of Veterans Affairs (DVA) health- care facilities have received mental health diagnoses.16 Given that OEF/OIF veterans now are eligible for 5 years of free mil- itary service-related health care through the DVA Healthcare System, a better understanding of factors related to psychiat- ric symptoms in this population is needed to facilitate early assessment and effective treatments.
A recent study examined the International Classi?cation of Diseases, Ninth Revision, Clinical Modi?cation (ICD-9-CM) codes in the DVA administrative and clinical data sets for over 100,000 OEF/OIF veterans evaluated in DVA Healthcare facilities between September 30, 2001 and December 31, 2005.16 The ?ndings indicated that a substantial portion of OEF/OIF veterans who accessed DVA care had co-occurring mental health diagnoses and psychosocial problems, with younger veterans (age 18?24 years) at the highest risk for
Trauma Exposure and Physical Injury
PTSD, compared to veterans 40 years and older.16 This study, however, was not able to address the role of military branch, rank, and combat exposure as potential confounders of the relationship between age and mental health problems. Here, we report on a similar, albeit smaller, sample of OEF/OIF veterans and reservists registering for care at the Veteran Affairs (VA) San Diego Healthcare System. In addition to men- tal health questionnaires, newly registered veterans provided information on most recent branch of service, rank, combat and trauma exposure, and combat-related injury with the goal of more comprehensively characterizing the OEF/OIF men- tal health concerns. We examined the relationships between demographic factors, military service characteristics, combat- related injury, and mental health symptoms. We hypothesized that most recent branch of service and injury during combat would predict PTSD status, after controlling for demographic and service variables such as age, gender, race, and rank.
METHODS
Study Population
During a 6-month period from April to October 2006, 449 newly registered OEF/OIF veterans and reservists, con- secutively enrolled for general care in the VA San Diego Healthcare System, were approached at Member Services (initial registration) to complete a battery of questionnaires. Among these included 339 OEF/OIF newly registered veter- ans and reservists who completed all data, representing 76% of the total sample. The remainder of the sample (n = 110) had missing data on some variables of interest and were there- fore excluded from the analyses reported here. The study was approved by the University of California Institutional Review Board and by the VA San Diego Healthcare System?s Research and Development Committee.
Source of Data
Participants completed a packet of questionnaires, which included data on age, gender, race, rank, and most recent branch of service. They were asked one question about injury: if they had been physically injured during combat (yes, no). We did not speci?cally inquire about head, versus other types of combat-related injury.
In addition, the commonly used and well-validated Combat Exposure Scale (CES),17 Davidson Trauma Scale (DTS),18 Alcohol Use Disorders Identi?cation Test (AUDIT),19 and Drug Abuse Screening Test (DAST)20 were included in the packet. Given the DTS was the primary measure of interest, and because the packet was administered to all participants, there was the potential that this measure would be completed erroneously by participants who had not experienced trauma. To minimize error variance, a skip-out item was generated and placed before this measure, asking, ?Have you ever expe- rienced a traumatic event?? A response of ?yes? led the par- ticipant to complete the DTS, a response of ?no? instructed participant to ?skip out? of this measure. As per the original
DTS instructions, participants were then prompted to, ?Please identify the trauma that is most disturbing to you? and wrote a brief description of their experience.
Also included in the packet was a 2-item yes/no depres- sion screener that asked: (1) During the past month have you often been bothered by feeling down, depressed, or hopeless?
(2) During the past month have you often been bothered by little interest or pleasure in doing things? Use of this ?2-item depression screener? is standard practice within the VA system to quickly identify patients who are in need of more thorough assessment. This 2-item screener has been routinely utilized in other studies published on VA populations as a general screen for depression,21 and has been found to be a psychometrically sound and useful measure for detecting depression in primary care settings.22 Further, the measure has demonstrated similar test characteristics to other case-?nding instruments (including the Beck Depression Inventory) and is less time consuming.22
A positive screening for PTSD was de?ned as endorsement of trauma exposure and DTS score of greater than or equal to
40.18 Substance abuse ?caseness? was de?ned by a positive screen (2 or more) on the DAST or a positive screen (5 or more) on the AUDIT. Finally, depression caseness was deter- mined by veteran endorsement of both depressed mood and anhedonia in the past 1 month.
Statistical Analyses
Descriptive statistics were used to assess the prevalence of mental health symptoms. Pearson c 2 tests were used to com- pare the prevalence for these symptoms in veterans who did and did not report a trauma event. Logistic regression analy- sis was performed to predict presence of PTSD and determine odds ratios (OR) and 95% con?dence intervals (CI) associated with demographic, military, and combat injury characteris- tics. Covariates and factors were entered stepwise in 3 blocks. Block one consisted of demographic characteristics (age, gen- der, race). Block 2 consisted of military characteristics (most recent branch of service and rank). Rank was dichotomized as
(1) E5 or less and (2) noncommissioned of?cers E6 or higher and commissioned of?cers. Block 3 consisted of injury during combat. We applied one-way analyses of variance and Pearson c 2 tests to determine relationships between variables predic- tive of PTSD and (1) exposure to combat and (2) self-report of trauma event (combat and noncombat). Finally, we performed one-way analysis of variance and independent sample t tests to determine if there were differences in age by PTSD status, rank, and branch of service. Signi?cance level was set at p ?
0.05. All analyses were conducted using Statistical Package for Social Sciences (SPSS) version 15.0.23
RESULTS
Characteristics of the Newly Enrolled OEF/OIF Veterans
Table I lists the demographic and military service-related characteristics of 339 veterans and reservists enrolled for
