Active military service in the US may reduce, not increase, risk of depression

In a groundbreaking observational study recently published in BMJ Military Health, researchers have uncovered evidence that challenges long-held perceptions regarding the relationship between military service and mental health outcomes, specifically the risk of depression. Contrary to prevailing assumptions that military experience, particularly combat exposure, increases vulnerability to depressive disorders, this comprehensive analysis suggests that serving in the US military may actually confer a protective effect against depression. The findings stand to reshape the narrative around military service and mental health, provoking renewed inquiry into the psychological and sociological dimensions of military life.

The study taps into data gathered from the US National Health and Nutrition Examination Survey (NHANES), covering the period from 2011 through 2023. NHANES is renowned for its nationally representative sampling methodology, designed to reflect the broader American population across various demographics and health statuses. By analyzing five cycles of survey data, the investigators were able to rigorously compare depression prevalence among individuals with military service backgrounds to those without, while controlling for numerous confounding factors such as age, sex, race, socioeconomic status, and comorbid health conditions.

Central to the assessment of depressive symptoms was the Patient Health Questionnaire (PHQ-9), a clinically validated instrument widely employed in psychiatric epidemiology. The PHQ-9 evaluates the presence and severity of nine hallmark depressive symptom domains over the preceding two weeks, rating frequency on a scale of 0 (“not at all”) to 3 (“nearly every day”). Clinical significance was determined using a threshold score of 10 or above, indicative of at least moderate depression requiring professional attention. This quantifiable approach ensures robust and interpretable mental health metrics, facilitating population-level comparisons.

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Among the 25,949 survey participants, 2,407 individuals reported prior US military service. Statistical weighting extrapolated these figures to represent approximately 8.8 million military-experienced adults nationwide. The remaining cohort of 23,542 participants without military affiliation corresponded to roughly 89 million US adults. Depression, as defined by the PHQ-9 criteria, was identified in 2,548 respondents overall. The unadjusted prevalence of depression across the entire sample was nearly 9.5%, yet notably, it was lower—about 7.5%—among those with a history of military service.

To unravel the complexity behind these numbers, the research team employed multivariate regression analyses to adjust for a suite of potential confounders including demographic variables, income levels, educational attainment, marital status, and prevalent metabolic conditions like hypertension, hypercholesterolemia, and diabetes. After rigorous statistical adjustment, military service was associated with a statistically significant 22 to 23% relative reduction in depression risk compared to individuals with no military experience. This protective effect persisted even after further controls were introduced for physical health comorbidities.

Examining the veteran subpopulation separately, the study found no significant difference in depression rates compared to the general population when unadjusted. However, refined analyses revealed that female veterans and those who were unmarried or divorced faced elevated depression risks. Conversely, high income and healthier cardiovascular profiles appeared to mitigate such risks. Interestingly, active duty status itself did not emerge as a significant independent predictor of depression, challenging stereotypes that ongoing service inherently predisposes individuals to poor mental health outcomes.

It is imperative to emphasize that this investigation is observational and cross-sectional by design, meaning causality cannot be definitively inferred. The researchers acknowledge that essential variables such as combat exposure intensity, length of military service, trauma history, and specific deployment experiences were not captured in the NHANES dataset and likely influence mental health trajectories profoundly. Furthermore, psychiatric outcomes are multifactorial, involving complex interactions between genetic predispositions, psychological resilience, social supports, and environmental stressors.

Nevertheless, the study authors propose that the structured environment, camaraderie, discipline, and coping mechanisms honed during military service may foster psychological resilience, potentially offsetting some traditional stressors associated with military life. This hypothesis aligns with developmental psychology theories positing that controlled exposure to adversity can stimulate adaptive growth when supported by protective social networks. The military’s emphasis on unit cohesion and identity formation might provide essential buffers against depressive symptomatology.

The findings also highlight a critical methodological consideration: prior research demonstrating higher depression rates in veterans has often been limited to healthcare system-based samples, which may be biased toward individuals actively seeking medical and mental health care, thus overestimating population prevalence. By utilizing NHANES, which samples the civilian community at large, this study offers a less biased lens through which to evaluate mental health burdens associated with military service, potentially reconciling conflicting epidemiological data.

This nuanced understanding invites policymakers, clinicians, and military leadership to reconsider strategies targeting mental health interventions within armed forces and veteran populations. It underscores the importance of tailored approaches that recognize variability in risk profiles linked to gender, marital status, and socioeconomic factors rather than blanket assumptions about service-related mental health impairments. Equally, it prompts further research into identifying protective elements within the military culture and training that could be leveraged in broader mental health promotion efforts.

In sum, this extensive cross-sectional study advances a compelling argument that, contrary to widespread belief, general US military service does not inherently increase depression risk and may, under certain circumstances, be protective. While it stops short of establishing causality, its breadth and representativeness provide a robust platform for re-examining military mental health paradigms and underscore the complexities inherent in understanding how service shapes psychological well-being across the lifespan.

Subject of Research: People
Article Title: Military service and depression risk among American adults: a cross-sectional analysis based on NHANES data from 2011 to 2023
News Publication Date: 29-May-2025
Web References:
NHANES: https://www.cdc.gov/nchs/nhanes/index.html
PHQ-9: https://patient.info/doctor/patient-health-questionnaire-phq-9
References: 10.1136/military-2024-002932
Keywords: Affective disorders, Environmental illness, Environmental health, Government jobs, Warfare

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