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Our paper, “Mental health over time in a military sample: the impact of alcohol use disorder on trajectories of psychopathology after deployment,” examined a sample of Ohio National Guard members across four years of interviews. All soldiers in our sample were deployed within two years of the baseline survey and experienced a traumatic event during that deployment.

We modeled trajectories of posttraumatic stress and depression symptoms after these events in order to see how symptoms unfold over time. Trajectories of mental health have been predominately studied in civilian populations following exposure to mass traumas such as hurricanes or terrorist attacks (Nandi, Tracy, Beard, Vlahov, & Galea, 2009; Pietrzak, Van Ness, Fried, Galea, & Norris, 2013), and many have documented the following groupings of symptoms as latent classes: resilient (initial symptomology followed by recovery), resistant (consistently low symptomology), and chronic dysfunction groups (consistently high symptomology), together with more variable relapsing/remitting groups (Bonanno et al., 2012; Norris, Tracy, & Galea, 2009). 

We found very similar trajectory groups to the ones described above; the majority of our participants were resistant to both posttraumatic stress and depression symptoms. The next largest groups were resilient for both outcomes, and the smallest groups had chronically high symptoms. Additionally, we observed a group that had increasing symptoms for depression across the four years, and a group that showed constant, mild symptoms across the four years for posttraumatic stress.

We also modeled time-stable risk factors (measured at baseline) and time-varying covariates (measured at each time point) to see how they affected group membership and trajectory shape. We found that being non-married and having low education were associated with membership in the resilient depression and posttraumatic stress groups respectively, compared to membership in the resistant groups. Being deployed to an area of conflict (Afghanistan or Iraq) was associated with higher-symptom trajectory groups for both outcomes. Having a high number of lifetime stressors and traumatic events was associated with high-symptom groups for depression and posttraumatic stress respectively.

Lastly, we were interested in alcohol use disorder specifically as a time-varying covariate because it is known to co-occur with both posttraumatic stress and depression (Thomas et al., 2010), and also to be highly prevalent among military samples (Bray et al., 2010; Cohen, Fink, Sampson, & Galea, 2015). We found that alcohol use disorder at all time points was associated with an increase in both depression and PTS symptoms, with the largest effect seen on the already higher-symptom trajectory groups. For the increasing depression symptom group, alcohol use disorder contributed to a steeper increase in symptoms as more time passed since their initial deployment. In contrast, the depression-resilient group actually experienced a smaller effect of alcohol use disorder as more time from their deployment passed, suggesting that resilience toward depression symptoms after a deployment experience may put individuals in a better position to be resilient to the effect of alcohol use disorder on depression as well.

In general, our findings illustrate how the cumulative effect of alcohol use disorder may manifest in a higher burden of psychopathology at multiple time points across a study period. This is important considering that alcohol use disorder has been documented as a modifiable risk factor in U.S. service members (Pemberton et al., 2011). Limitations include loss to follow-up across the four years and inability to make any causal inferences (see discussion question 1). Future studies might model trajectories with other time-varying covariates, or in different military samples, such as among active duty soldiers or female soldiers.

Discussion Questions:


  1. Is it possible that posttraumatic stress and depression are causing alcohol use disorder to occur or worsen, instead of alcohol use disorder contributing to higher posttraumatic stress and depression symptoms, as our models suggest? Or some combination?
  2. Would you expect to see similar trajectories in a sample of active-duty soldiers, or soldiers from a different era?
  3. Do you think gender might play a role in trajectories? Our sample is predominately male, but might a sample with more women find similar results?


Reference Article:  

Sampson, L., Cohen, G. H., Calabrese, J. R., Fink, D. S., Tamburrino, M., Liberzon, I., . . . Galea, S. (2015). Mental Health Over Time in a Military Sample: The Impact of Alcohol Use Disorder on Trajectories of Psychopathology After Deployment. Journal of Traumatic Stress, 28(6), 547-555. doi: 10.1002/jts.22055

Author Bio: 

Laura Sampson is a PhD student and statistical analyst in the Department of Epidemiology at the Boston University School of Public Health. Her research interests include mental health in the military, after natural disasters, and in megacities.


Bonanno, G. A., Mancini, A. D., Horton, J. L., Powell, T. M., Leardmann, C. A., Boyko, E. J., . . . Smith, T. C. (2012). Trajectories of trauma symptoms and resilience in deployed U.S. military service members: prospective cohort study. British Journal of Psychiatry, 200, 317-323. doi: 10.1192/bjp.bp.111.096552
Bray, R. M., Pemberton, M. R., Lane, M. E., Hourani, L. L., Mattiko, M. J., & Babeu, L. A. (2010). Substance use and mental health trends among U.S. military active duty personnel: key findings from the 2008 DoD Health Behavior Survey. Military Medicine, 175, 390-399. doi: 10.7205/MILMED-D-09-00132
Cohen, G. H., Fink, D. S., Sampson, L., & Galea, S. (2015). Mental health among Reserve Component military service members and veterans. Epidemiologic Reviews. doi: 10.1093/epirev/mxu007
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Pemberton, M. R., Williams, J., Herman-Stahl, M., Calvin, S. L., Bradshaw, M. R., Bray, R. M., . . . Mitchell, G. M. (2011). Evaluation of two web-based alcohol interventions in the U.S. military. Journal of Studies on Alcohol and Drugs, 72(3), 480-489. doi: 10.15288/jsad.2011.72.480
Pietrzak, R. H., Van Ness, P. H., Fried, T. R., Galea, S., & Norris, F. H. (2013). Trajectories of posttraumatic stress symptomatology in older persons affected by a large-magnitude disaster. Journal of Psychiatric Research, 47(4), 520-526. doi: 10.1016/j.jpsychires.2012.12.005
Thomas, J. L., Wilk, J. E., Riviere, L. A., McGurk, D., Castro, C. A., & Hoge, C. W. (2010). Prevalence of mental health problems and functional impairment among active component and National Guard soldiers 3 and 12 months following combat in Iraq. Archives of General Psychiatry, 67(6), 614-623. doi: 10.1001/archgenpsychiatry.2010.54