Occurrence of Psychiatric Conditions or Symptoms after Military Service-related Environmental and Chemical Toxic Exposures: An Evidence Map

The report is a product of the VA/HSR Evidence Synthesis Program.

Occurrence of Psychiatric Conditions or Symptoms after Military Service-related Environmental and Chemical Toxic Exposures: An Evidence Map

Takeaway: This evidence mapping review highlights psychological and neurocognitive symptoms and diagnoses associated with military toxic exposures, as well as key gaps in the literature. Available evidence suggests that Veterans with a high likelihood of toxic exposure during military service could be expected to present with relatively high levels of mental health and neurocognitive symptoms and diagnoses. The studies reviewed had a diversity of methodological approaches, making it difficult to integrate data sources. Study samples were often White and male and were therefore not largely representative of diverse military service members.

U.S. service members face many possible toxic exposures (e.g., biological and chemical agents, airborne hazards, radioactive materials), but the prevalence of psychological and neurocognitive conditions and symptoms among exposed Veterans has not been well characterized. The Sergeant First Class Heath Robinson Honoring our Promise to Address Comprehensive Toxics (PACT) Act broadens VA healthcare eligibility for Veterans with conditions associated with military toxic exposures, likely leading more Veterans with presumed toxic exposures to access VA care. At this time, the mechanisms that might link toxic exposures and mental health among Veterans are unclear; the concordance between these exposures and outcomes appears high. Understanding what mental health services and other resources may be needed to support Veterans with military toxic exposure will be crucial for future healthcare planning.

HSR's Evidence Synthesis Program (ESP) Center in Durham, NC, created an evidence map to help VHA clinical teams provide informed care to Veterans who present with psychological and neurocognitive concerns during toxic exposure screenings, and will help develop national guidance for approaches to screening, assessment, and treatment related to these concerns. The evidence map also identified gaps in the literature to inform future VHA research efforts.

Investigators searched for relevant peer-reviewed articles in MEDLINE, Embase, APA PsycINFO, and PTSDpubs through July 27, 2023. Eligibility was limited to studies that examined environmental exposures that occurred during military service and the prevalence of, or association with, psychiatric or neurocognitive diagnoses or symptoms. Studies were also required to include at least 100 Veteran participants and were excluded if they focused only on pyridostigmine bromide (PB) pills or prophylactic vaccinations given during military service.

Summary of Findings

Of the 49 primary studies that met eligibility criteria, 41 reported disaggregated psychiatric or neurocognitive outcomes; 17 reported neurocognitive symptoms, diagnosis, or measures; 19 reported psychiatric diagnoses; and 30 reported psychiatric symptoms. Most of the included studies were conducted among Persian Gulf War Veterans, and most of the studies that reported sociodemographic composition of the study samples predominantly enrolled male, White Veterans. There was extensive variation in how exposures and outcomes were defined and measured across studies. Often studies did not quantify the duration, frequency, or severity of exposure and many only used one item from a multi-item health questionnaire to capture complex mental health constructs. Most exposure and symptom data were based on self-reports.

Other notable results included the following:

• Chemical exposures were the most frequently examined military toxic exposures.
• Depression and PTSD were the most reported psychiatric outcomes. Few studies reported other important psychiatric outcomes, such as suicidality and substance misuse.
• Camp Lejeune contaminated water, radiation, and heavy metals were understudied military toxic exposures.
• Few studies included women Veterans and those from underrepresented racial and ethnic groups.
• Large to moderate associations were frequently observed between PTSD symptoms and chemical exposures, smoke from oil fires and burn pits, and multiple/mixed exposure types.
• A small body of literature (3 studies) suggests a moderate to strong association between military-related Agent Orange exposures for Vietnam-era Veterans and psychotic disorders and psychosis symptoms.
• Only 9 studies assessed neurocognitive functioning as an independent construct, making it difficult to discern the association between military toxic exposures and neurocognitive function.
• Despite multiple gaps in the literature, available evidence suggests that Veterans with a high likelihood of environmental toxic exposures during military service may be expected to later present with relatively high levels of mental health needs.

Implications

In the coming decades, many Veterans will have mental health and/or neuropsychiatric needs that VHA providers will be asked to meet. The available evidence suggests that Veterans with a history of military toxic exposures are likely to present with relatively high levels of mental health needs, particularly PTSD. Whether the association between toxic exposure and mental health proves to be causal, the PACT Act's expansion of VA healthcare creates an immediate and urgent need to better understand the mental health needs of Veterans currently served by VHA, as well as Veterans with a history of toxic exposure who may seek VHA services in the future.

Limitations

• The review did not synthesize outcome data into summary estimates and did not conduct a critical appraisal of the included studies' methodology.
• The existing research on military toxic exposures and mental health/neuropsychiatric outcomes has several important limitations, including inconsistency in measurement, subjective assessment of exposures and outcomes, and the inclusion of primarily White, male identifying Veterans.
• Studies identified by this review cannot address or confirm a direct causal relationship between military-related toxic exposures and adverse psychiatric or neurocognitive outcomes.

Future Research

Future research should incorporate multiple sources of data (e.g., medical records, military records, and objective neuropsychological tests) to increase the reliability and validity of exposure, neuropsychological symptoms, and diagnosis variables. Additionally, future work should more robustly explore certain exposures (e.g., Camp Lejeune contaminated water, radiation, heavy metals) and use samples that are more representative of the modern active-duty and Veteran populations (e.g., women, racially diverse participants, and Veterans deployed post-9/11).

Nugent SM, Magnante AT, Leflore-Lloyd N, Bourassa KJ, Meckes SJ, Gordon AM, Boyle SH, Chen D, Alishahi Tabriz A, Wells SY, Jacobs M, Snyder J, Yang L, Cantrell S, Goldstein KM, Gierisch JM. Occurrence of Psychiatric Conditions or Symptoms after Military Service-related Environmental and Chemical Toxic Exposures: An Evidence Map. Washington, DC: Evidence Synthesis Program, Health Services Research and Development Service, Office of Research and Development, Department of Veterans Affairs. VA ESP Project #09-010; 2024.

To view the full report, go to vaww.hsrd.research.va.gov/publications/esp/MHTE.cfm (intranet only).

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