The association between a priori dietary patterns and psychological disorders in military personnel

**Background:** Military personnel experience high rates of mental health disorders including depression, anxiety, and stress, which impair performance and increase suicide risk. Diet is a modifiable risk factor, but evidence on whole-diet patterns in military populations is limited. This study examined associations between four a priori dietary patterns (DASH, Mediterranean diet, DII, and HEI-2015) and odds of depression, anxiety, and stress in Iranian military staff.

**Methods:** A cross-sectional study was conducted on 400 male military personnel (mean age 38.67 ± 5.22 years, range 30–60) recruited from Iranian military centers between September 2020 and January 2022. Dietary intake was assessed using a validated 168-item semi-quantitative food frequency questionnaire (FFQ). Adherence to DASH (score 8–40), MD (score 0–8), DII (based on 32 food parameters), and HEI-2015 (score 0–100) was calculated. Mental health was evaluated using the DASS-21 questionnaire, with cutoffs of ≥10 for depression, ≥8 for anxiety, and ≥15 for stress. Logistic regression was used to estimate odds ratios across quartiles of adherence, adjusting for daily energy intake, physical activity, BMI, age, smoking, marital status, and education level.

**Key Results:** The prevalence of depression, anxiety, and stress was 64.5%, 63.2%, and 61.3%, respectively. In the fully adjusted model (Model 3), individuals in the highest quartile of HEI-2015 adherence had significantly lower odds of anxiety compared to the lowest quartile (OR = 0.51, 95% CI: 0.27–0.96, p = 0.03). Higher adherence to DII was associated with a 2.74-fold increased odds of anxiety (OR = 2.74, 95% CI: 1.06–7.04, p = 0.03). For stress, only quartile 2 of HEI-2015 showed significantly lower odds compared to quartile 1 (p = 0.04), while quartile 4 showed no significant association. No significant associations were found between DASH, MD, or DII and stress, and none of the four dietary patterns were significantly associated with depression. The DASH and MD patterns showed no significant associations with any mental health outcome.

**Clinical Implications:** These findings suggest that promoting adherence to HEI-2015 guidelines and reducing consumption of pro-inflammatory foods (lower DII) may be effective nutritional strategies to reduce anxiety in military personnel. The lack of association with depression and the non-linear relationship between HEI-2015 and stress (significant only at moderate adherence) warrant further investigation. Limitations include the cross-sectional design (causality cannot be inferred), all-male sample (results not generalizable to women), potential residual confounding, and reliance on self-reported dietary data. Future prospective cohort studies including hormonal biomarkers (e.g., cortisol, serotonin) and female military personnel are needed.