Original Article
Millennium Cohort: The 2001–2003 baseline prevalence of mental disorders in the U.S. military

https://doi.org/10.1016/j.jclinepi.2006.04.008Get rights and content

Abstract

Objectives

The 12-month prevalence of common mental illnesses in the United States is estimated to be 26%, accounting for an increasing fraction of all disability in the general population. The U.S. military is a unique group involved in response and defense during times of conflicts and disasters. The mental health of service members affects organizational productivity and effectiveness and is of great importance to the health of U.S. military members and public health in general.

Study Design and Setting

In the present report, the authors describe the baseline prevalence of mental disorders in a large U.S. military cohort, the Millennium Cohort, established for a 22-year longitudinal study of the health effects of military service. Using crude and weighted prevalence and multivariable logistic regression, the mental health morbidity of the Millennium Cohort is reported for various demographics.

Results

These analyses suggest that although the cohort compares favorably to other populations, there are military subpopulations, including women, younger, less educated, single, white, short-term service, enlisted, and Army members, who are at greater odds for some mental disorders.

Conclusion

With ongoing U.S. involvement in combat operations around the world, these baseline data are essential to assessing long-term mental health morbidity in U.S. military service members.

Introduction

The 12-month prevalence of common mental illnesses among adults in the United States is estimated to be 26% [1]. This prevalence placed the United States highest out of 14 countries chosen from the Americas, Europe, the Middle East, and Asia. The United States also ranked highest in severe disorder prevalence (7.7%) [1]. Mental disorders accounted for nearly 11% of the disease burden worldwide in 1990, ranking these afflictions almost as harmful to public health as cardiovascular and respiratory diseases [2]. In a subsequent 2001 World Health Report focusing on mental health, the global burden of disease from mental disorders was estimated to have increased to 12% and projected to reach 15% by 2020 [3]. This report further documented circumstances or characteristics associated with increased mental health disorders, including poverty, sex, age, major physical diseases, family or social environment, and conflicts or disasters [3].

The U.S. military is frequently called upon as the first line of response or defense in conflicts and disasters, often resulting in service members' separation from family or home life for extended periods of time. When service-related risk factors known to be associated with increased mental health morbidity are considered in conjunction with normal population risk factors, the mental health of this population becomes a topic of much concern. Hoge et al. [4] reported that 13% of all military hospitalizations and 28% of all military hospital bed days from 1990 to 1999 were due to mental disorders, and nearly half of those with a first time mental disorder hospitalization separated from military service within 6 months. Reports have suggested that personnel involved in combat operations or peacekeeping missions following combat may have increased symptoms of psychological distress [5], [6], [7], [8], [9], [10], [11], [12], with one report recently suggesting significant risk of mental health problems after combat duty in Iraq and Afghanistan [13]. With America's dependence on a fit and healthy force for the security of this nation, maintaining sound mental health of all military personnel is one of the primary goals of military medicine.

The mental health of military service members affects organizational productivity and effectiveness and is of great importance to the U.S. military for retention, readiness, and mission capability. The military is also committed to protecting the health, both physical and mental, of all service members. In this report, the authors describe the baseline prevalence of mental disorders in a large U.S. military cohort that will be longitudinally followed until 2022.

Section snippets

Study population

The methodology for the Millennium Cohort Study has been described in detail elsewhere [14]. In brief, those invited to participate in the Millennium Cohort Study came from a sample provided by the Defense Manpower Data Center (DMDC), Seaside, California, representing approximately 11.3% of the 2.2 million men and women in service as of October 1, 2000. U.S. military personnel serving in the Army, Navy, Coast Guard, Air Force, and Marine Corps were selected and oversampled for those previously

Results

Demographic data for this report were complete and available for 76,476 of 77,047 (99.3%) Millennium Cohort respondents. The cohort consisted of 73% men, 68% between 25 and 44 years of age, 51% with at least some college experience, 63% married, 70% white non-Hispanic, 30% recently deployed, 45% with less than 10 years of military service, 77% enlisted personnel, 57% active duty, 48% Army, and 20% combat specialists (Table 1). When compared with the U.S. military demographic and military

Discussion

The worldwide prevalence of mental disorders has increased significantly during the past two decades and the projected 15% prevalence by 2020 [3] will have far-reaching public health implications [31]. The complex nature of identifying mental disorders, coupled with multiple causal pathways and diverse populations in which these conditions present, make this a likely underestimate of the true burden of disease. The U.S. military represents the diversity of the U.S. population with varying

Acknowledgments

We thank Scott L. Seggerman from the Management Information Division, Defense Manpower Data Center, Seaside, California, for providing a sample of military personnel and their demographic and deployment data. Additionally, we thank Isabel Gomez, Gia Gumbs, Sheila Jackson, Cynthia Leard, Travis Leleu, Nick Martin, Robb Reed, Steven Spiegel, Jim Whitmer, and Dr. Sylvia Young from the Department of Defense Center for Deployment Health Research, Naval Health Research Center, San Diego, California,

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  • Cited by (0)

    In addition to the authors, the Millennium Cohort Study Team is composed of Margaret A.K. Ryan,1 Tomoko I. Hooper,2 Gregory C. Gray,3 Gary D. Gackstetter,2 Edward J. Boyko,4 and Paul Amoroso5 from the 1Department of Defense Center for Deployment Health Research at the Naval Health Research Center, San Diego, CA, USA; 2Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, MD, USA; 3Department of Epidemiology, College of Public Health, University of Iowa, Iowa City, IA, USA; 4Seattle Epidemiologic Research and Information Center, Veterans Affairs Medical Center, Puget Sound, Seattle, WA, USA; and 5Army Research Institute of Environmental Medicine, Military Performance Division, Natick, MA, USA.

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