American Journal of Epidemiology Published by the Johns Hopkins Bloomberg School of Public Health 2008. Letter to the Editor RE: ‘‘PSYCHIATRIC DIAGNOSES IN HISTORIC AND CONTEMPORARY MILITARY COHORTS: COMBAT DEPLOYMENT AND THE HEALTHY WARRIOR EFFECT

The Journal article by Larson et al. (1) offers new data regarding utilization rates of psychiatric diagnoses in mili-tary cohorts. However, crucial information, well known to professionals with knowledge of the military mental health care system and not adequately addressed in the article or accompanying editorial (2), likely renders the results invalid. To begin with, the time periods used in rate calculations were not equivalent. Although the total study period was identical for all 3 contemporary cohorts (July 2001– September 2005), the electronic medical record system used to access data did not capture health care in the combat environment. Consequently, for members of the combat-deployed cohort, mental health care utilization would be zero during the time of their deployment(s), with the excep