Relationship Between MTBI History And Depressive Symptoms Among Special Operations Forces Soldiers

PURPOSE: Increased mild traumatic brain injury (mTBI) incidence has been related to higher depressive mental health symptom burden among military servicemembers (SMs). This study’s purpose was to examine this relationship in a cohort of Special Operations Forces (SOF) Soldiers. METHODS: In total, 196 male SOF Soldiers self-reported clinician-diagnosed mTBI and depressive symptoms through an electronic questionnaire. The Patient Health Questionnaire-9 (PHQ-9) measured depressive symptoms and asked participants to indicate their experience with nine items over the course of the past two weeks on a scale from 0 (“Not at all”) to 3 (“Nearly every day”). These items were then summed to derive a total symptom score (possible range: 0-27). Soldiers were categorized as reporting no mTBI (n = 109), 1 prior mTBI (n = 46), or 2+ prior mTBI (n = 41). Sample proportions were computed for depression severity clinical cutoff scores (none, mild, moderate, and severe). Wilcoxon rank sum tests compared PHQ-9 total scores between those with (n = 109) and without a mTBI history (n = 87), and a Kruskal-Wallis test was then used to compare PHQ-9 scores between mTBI history groups (0, 1, 2+). RESULTS: Overall, SOF Soldiers reported low depressive symptoms (3.0 ± 3.8, range = 0 to 24) on the PHQ-9 scale. Based on PHQ-9 clinical cutoff scores, most individuals were in the “none” (n = 145 range: 0-4) or “mild” (n = 37, range: 5-9) depressive symptoms category, with few in the moderate (n = 12, range: 10-14) or severe (n = 2, range: 15-27) categories. We did not observe any differences in depression scores (W = 4382.5; P = 0.354) between Soldiers with no prior mTBI (2.8 ± 3.4) and those with ≥1 mTBI (3.3 ± 4.2). Additionally, we did not observe any differences in PHQ-9 total scores between those with 0, 1, or 2+ prior mTBI (χ2(2) = 4.26, P = 0.097). CONCLUSIONS: Greater mTBI incidence was not associated with higher depression scores among SOF Soldiers. Future investigations can examine other factors, such as the traumatic events that may surround incident mTBI, and how they may contribute to depression symptoms. Funded by US Special Operations Command