Journal of Traumatic Stress, Vol. 00, No. 0, 2010, pp. 1–8 ( C  2010) A Comparison of OEF and OIF Veterans and Vietnam Veterans Receiving Cognitive Processing Therapy Kathleen M. Chard and Jeremiah A. Schumm Cincinnati VA Medical Center and Department of Psychiatry, University of Cincinnati, Cincinnati, OH Gina P. Owens University of Tennessee, Knoxville, TN Sara M. Cottingham Xavier University, Cincinnati, OH The current wars in Iraq and Afghanistan are producing large numbers of veterans who have experienced a variety of combat stressors. The potential impact of combat exposure has been established, including significant rates of posttraumatic stress disorder (PTSD). Limited research has examined potential differences between veteran groups and one study to date has examined differences between eras in terms of treatment response. The present study seeks to examine cohort differences between Operation Enduring Freedom and Operation Iraqi Freedom veterans and Vietnam veterans (N = 101) before and after completing treatment for PTSD using cognitive processing therapy. Findings suggest that veterans from these eras responded differently to treatment and there are multiple variables that should be considered in future cohort studies. The current wars in Iraq and Afghanistan are producing large numbers of veterans who have been exposed to a variety of combat stressors, including shootings, rocket attacks, and bomb- ings. The potential impact of combat exposure on the mental health of returning veterans of various service eras has been es- tablished (Dohrenwend et al., 2006; Koenen, Stellman, Sommer, & Stellman, 2008; Southwick et al., 1993). Vietnam veterans have been the focus of much mental health research investigating the impact of combat exposure (Kulka et al., 1990), the poten- tial long-term effects of combat and posttraumatic stress disorder (PTSD; Koenen et al., 2008), and the PTSD treatment process (Elliott, Biddle, Hawthorne, Forbes, & Creamer, 2005). Recent research suggests that military personnel serving in Operation En- during Freedom (OEF) and Operation Iraqi Freedom (OIF) return with similar mental health concerns to previous eras, including PTSD, depression, substance abuse, and generalized anxiety dis- order (Felker, Hawkins, Dobie, Gutierrez, & McFall, 2008; Hoge et al., 2004; Jacobson et al., 2008). Comparisons between Vietnam-era and OEF- and OIF-era veterans are limited, but have recently begun to explore poten- tial differences between these groups in mental health and treat- ment outcome (e.g., Fontana & Rosenheck, 2008). Fontana and Rosenheck (2008) found in a contemporaneous treatment-seeking sample that included OEF and OIF veterans and Vietnam veterans Correspondence concerning this article should be addressed to: Kathleen M. Chard, Cincinnati VA Medical Center, PTSD and Anxiety Disorders Division, 3200 Vine Street, Cincinnati, OH 45220. E-mail: Kathleen.Chard@va.gov. C  2010 International Society for Traumatic Stress Studies. Published online in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/jts.20500 that OEF and OIF veterans had higher levels of PTSD symptoms at initial assessment than did Vietnam veterans. Further, results indicated that OEF and OIF veterans showed higher levels of improvement in treatment compared with their older Vietnam veteran counterparts (Fontana & Rosenheck, 2008). Other treat- ment outcome research (Rauch et al., 2009) suggests successful treatment using prolonged exposure for OEF and OIF veterans and Vietnam veterans; however, the sample size for this study was too small for comparisons in outcome by cohort. Multiple factors may produce differences in PTSD treatment outcome between OEF- and OIF-era and Vietnam-era veterans. Specific characteristics related to service era, such as the com- bat environment and homecoming reception may impact cohort differences in PTSD treatment outcome. The war in Vietnam was characterized by civilian guerilla warfare and over time, decreasing societal support for the war effort (Fontana & Rosenheck, 1994a; Friedman, 2005). Prior research has shown differences in types of combat exposure for Vietnam veterans compared with veterans of earlier war eras, particularly in the domain of witnessing or partici- pating in atrocities (Fontana & Rosenheck, 2008). Further, among Vietnam veterans, a negative homecoming reception, including a sense of lack of support from both society and family, has been a strong predictor of PTSD beyond combat exposure (Fontana & Rosenheck, 1994b; Johnson et al., 1997). Although resistance to 1