Cortical Volumes Did Not Associate With Mental Health Symptoms In Special Operations Forces Service Members

Abstract

Military service may lead to mental health consequences including depression, anxiety, and posttraumatic stress. Studies have identified associations among negative mental health symptoms and brain structure, including in the ventromedial prefrontal cortex (vmPFC). PURPOSE: To associate vmPFC volume with mental health symptoms. METHODS: Participants were 212 Special Operations Forces (SOF) combat Service Members (SMs) (age = 32.2 ± 3.7 years). Most SOF SMs were beginning their SOF career (n = 132, 62.3%), and a large minority had served for multiple years (n = 80, 37.7%). The SOF SMs self-reported concussion history [yes = 93 (50.3%); no = 92 (49.7%); 27 did not disclose]. They also reported mental health symptoms [depression (BSI-18 depression subscale), anxiety (GAD-7), posttraumatic stress (PCL-5), subjective well-being (MHC)] at a clinical research center via an online platform. Neuroimaging was collected at a biomedical research imaging center. The vmPFC volume was measured using 3.0-Tesla MRI scanners (Siemens MAGNETOM Prisma and Siemens Biograph mMR). Whole-brain T1-weighted 3D anatomical images (voxel size = 1.0 mm3, TR = 2300 ms, TE = 2.98 ms), acquired with magnetization-prepared rapid gradient echo were processed with FreeSurfer 7.1.0 cortical reconstruction and segmentation. All mental health outcome variables were skewed and discrete. Therefore, Poisson regression models were fit while controlling for total intracranial volume and concussion history. Statistical significance threshold was set at α = 0.05. RESULTS: Only 185 SMs had all data elements and were included in our analyses. The vmPFC volume did not significantly predict variance in depressive (χ2(1) = 0.39, p = 0.53), anxiety (χ2(1) = 1.50, p = 0.22), posttraumatic stress (χ2(1) = 0.95, p = 0.33), or well-being (χ2(1) = 0.62, p = 0.43) symptoms. CONCLUSION: Previous findings linking vmPFC volume to mental health symptoms were not replicated in our SOF SMs. Mental health symptom variance was not explained by anatomic volume in a brain region key in emotion and social processing. It is possible that potential adverse effects of prolonged military service may result in a different relationship between these factors and outcomes. Funded by US Special Operations Command