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Posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) commonly co-occur among combat veterans (Stander, Thomsen, & Highfill-McRoy, 2014). This comorbidity is associated with greater distress and higher social and economic costs (Kramer, Booth, Han, & Williams, 2005). In the population of combat veterans, who have deployed to areas of military conflict under adverse circumstances, it is critical to understand the potential role of peripheral adverse social and interpersonal events that may increase risk for developing comorbid depression. Further, clinicians need to consider the timeframe of occurrence of such adverse social and interpersonal events in relation to combat deployment cycle. This understanding could assist with the development of prevention and intervention efforts.

To better understand these relationships, researchers conducted a secondary-analysis of 223 treatment seeking U.S. veterans with combat-PTSD who had deployed to Iraq and Afghanistan. The average age of the sample was approximately 34. The sample was 58% White and 84% non-Hispanic. Close to half were married (49%). Mean years of education was 13.75 and about half (51%) were currently working full-time.  Approximately two-thirds (69%) had deployed more than once and most (86%) had served as active duty armed forces (vs. National Guard or Reserves). The researchers administered a diagnostic clinical interview, a patient self-report measure of depression, and the Deployment Risk and Resilience Inventory (DRRI; King, King, Vogt, Knight, & Samper, 2006). The DRRI is a multi-form, self-report assessment tool that assesses risk and resilience factors that occur before, during, and after combat deployments. The researchers were interested in various deployment cycle adversity and social support variables and their simultaneous associations with depression comorbidity and severity.

Results from the clinical diagnostic interviews revealed that over two-thirds of the sample (almost 70%) had comorbid MDD. In addition to having greater self-reported depression severity, those with comorbid MDD also had more severe PTSD symptoms. Importantly, there were no sex, age, race, or ethnicity differences between those with and without MDD. This study was not designed to test causal relationships or competing explanations for PTSD and depression comorbidity, but evidence from prior studies suggests that the relationship between PTSD and depression is likely bidirectional meaning that greater depression predicts greater PTSD severity (Koenen, Stellman, Stellman, & Sommer, 2003) and greater PTSD predicts greater depression severity (Ginzburg, Ein-Dor, & Solomon, 2010). However, in a review of this comorbidity in combat veterans, researchers (Stander et al., 2014) concluded that the evidence offered a more compelling argument that PTSD poses risk for the subsequent development of MDD rather than the other way around.

A primary finding of this study was that participants who endorsed having greater concerns about life and family disruptions during deployment and lower social support after deployment exhibited more severe major depression symptoms. A less robust finding was that general (non-sexual) harassment from within the military unit during deployment was also independently, positively associated with depression symptom severity. Researchers also examined the association between depression severity and pre-deployment stressful life events, adverse childhood experiences, unit social support while deployed, sexual harassment during deployment, and post-deployment stressors. Of note, no effects were found. Relatedly, none of the variables studied was shown to predict the presence of comorbid MDD.

Similarly, no causal conclusions can be drawn about the relationship between deployment stressors (i.e., family concerns, unit harassment, post-deployment social support) and depression severity and this relationship may be bidirectional. For example, life and family disruptions during deployment may lead to depression, perhaps due to perceived helplessness and reduced self-efficacy when separated from home and family.  Harassment from within one’s unit or from superiors may cause significant stress and depression when viewed as a violation of traditional military values such as loyalty (Nillni et al., 2014) or because of the unexpected nature of threat from fellow military service members previously deemed safe and trustworthy. Further, poor social support after deployment may increase depression.  This could be a consequence of a lost sense of purpose following the deployment or the lack of perceived belonging, which many service members experience as they attempt to reintegrate into civilian life. Alternatively, preexisting depression and its associated symptoms (e.g., social withdrawal, irritability, rumination), could lead to greater isolation and worsening of family and interpersonal problems during and after deployment.

Collectively, these findings suggest that deployment and post-deployment interpersonal strain are critical factors associated with depression severity in combat veterans with PTSD.  Future research is urgently needed to study the effect of interventions designed to optimize social and family support, especially for at-risk families and military service members. Additionally, post-deployment initiatives that directly address the experience of isolation and enhance social support may mitigate depression severity in returning service members. Further study of the efficacy of peer support, community integration, veteran outreach, and behavioral health interventions emphasizing social connection may be of further benefit to this at-risk population.


Ginzburg, K., Ein-Dor, T., & Solomon, Z. (2010). Comorbidity of post- traumatic stress disorder, anxiety and depression: A 20-year longitudinal study of war veterans. Journal of Affective Disorders, 123, 249–257. doi:10.1016/j.jad.2009.08.006

King, L. A., King, D. W., Vogt, D. S., Knight, J., & Samper, R. E. (2006). Deployment Risk and Resilience Inventory: A collection of measures for studying deployment-related experiences of military personnel and veterans. Military Psychology, 18, 89-120. doi:10.1207/s15327876mp1802_1

Koenen, K. C., Stellman, J. M., Stellman, S. D., & Sommer, J. F. (2003). Risk factors for course of posttraumatic stress disorder among Vietnam veterans: A 14-year follow-up of American Legionnaires. Journal of Consulting and Clinical Psychology, 71, 980-986. doi:10.1037/0022-006X.71.6.980

Kramer, T. L., Booth, B. M., Han, X., & Williams, D. K. (2005). Service utilization and outcomes in medically ill veterans with posttraumatic stress and depressive disorders. Journal of Traumatic Stress, 16, 211-219. doi:10.1023/A:1023783705062

Nillni, Y. I., Gradus, J. L., Gutner, C. A., Luciano, M. T., Shipherd, J. C., & Street, A. E. (2014). Deployment stressors and physical health among OEF/OIF veterans: The role of PTSD. Health Psychology, 33, 1281-1287. doi:10.1037/hea0000084

Stander, V. A., Thomsen, C. J., & Highfill-McRoy, R. M. (2014). Etiology of depression comorbidity in combat-related PTSD: A review of the literature. Clinical Psychologist Reviews34, 87–98. doi:10.1016/j.cpr.2013.12.002

Reference Article

Goetter, E.M., Hoeppner, S.S., Khan, A.J., Charney, M.E., Wieman, S., Venners, M.R., Avallone, K.M., Rauch, S.A.M. and Simon, N.M. (2020), Combat‐Related Posttraumatic Stress Disorder and Comorbid Major Depression in U.S. Veterans: The Role of Deployment Cycle Adversity and Social Support. Journal of Traumatic Stress.

Discussion Questions

  1. What modifications can be made to clinical practice to assess deployment cycle adversity and social support among military service members?
  2. What clinical interventions might you incorporate to mitigate depression severity in recently deployed service members who are seeking treatment?
  3. What broader social efforts could be undertaken to enhance deployment cycle resilience in military service members?


About the Author

Dr. Elizabeth Goetter is a clinical psychologist in the Department of Psychiatry at Massachusetts and an Assistant Professor at Harvard Medical School.  Her clinical and research interests center on the evidence-based treatment of PTSD, with a focus on evaluating ways to improve the delivery and accessibility of mental health treatments.