Military service may lead to negative mental health consequences. Previous research has identified subcortical structures including hippocampus and amygdala volumes as predictors of negative mental health symptoms. PURPOSE: To associate amygdala and hippocampus volumes with positive and negative mental health. METHODS: Participants included 212 Special Operations Forces (SOF) combat Service Members (SMs) (age=32.2±3.7 years). Participants were beginning their SOF career (n=132, 62.3%) or had served for multiple years (n=80, 37.7%). Ninety-three participants (50.3%) reported no concussion history (27 did not disclose self-reported history). Participants self-reported concussion history and mental health symptoms. Neuroimaging was obtained using 3.0-Tesla MRI scanners (Siemens MAGNETOM Prisma or Siemens Biograph mMR). Whole-brain T1- weighted 3D anatomical images, acquired with magnetization-prepared rapid gradient echo, were segmented for subcortical structure volumes using FreeSurfer 7.1.0. Mental health symptom outcome scores were skewed and discrete. Thus, Poisson regression analyses were fit to test the relationships among hippocampal and amygdala volumes with mental health symptoms while controlling for total intracranial volume and concussion history. RESULTS: Only 185 SMs had all data elements and were included in our analyses. Amygdala volume was negatively associated with greater depressive symptom burden (χ²(1)=4.20, p=0.04) while hippocampal volume was not (χ² (1)=0.63, p=0.43). Neither hippocampal nor amygdala volumes were significantly associated with anxiety (χ² (1)=0.81, p=0.37, and χ² (1)=2.18, p=0.14, respectively), posttraumatic stress symptoms (χ² (1)=0.01, p=0.91 and χ² (1)=1.05, p=0.31, respectively), or subjective well-being symptoms (χ² (1)=0.04, p=0.84, and χ² (1)=0.26, p=0.61, respectively). CONCLUSION: Smaller amygdala volumes may predict increased depressive symptom risk in SOF SMs, which may deter current combat readiness and lead to poor long-term mental health outcomes. Future studies should continue to explore how objective neuroimaging data may predict behavioral outcomes among SOF Service Members. [ABSTRACT FROM AUTHOR]