Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access
Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc
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Original Article

Volume 18, Number 2, February 2026, pages 107-119

Dietary Behavior and Risk of Depression: Effects of Ultra-Processed Food and Water Intake in a National Sample of the United States

Figures

↓  Figure 1. STROBE flow diagram (NHANES 2021–2023).
Figure 1.
↓  Figure 2. Odds of PHQ-9–based depression by ultra-processed food intake quartiles. Models adjusted for age, sex, and body mass index. PHQ-9: Patient Health Questionnaire-9.
Figure 2.
↓  Figure 3. Odds of PHQ-9–based depression by ultra-processed food intake and water intake quartiles. Models adjusted for age, sex, and body mass index. PHQ-9: Patient Health Questionnaire-9.
Figure 3.
↓  Figure 4. Odds of PHQ-9–based depression by ultra-processed food and water intake quartile after excluding participants with extreme body mass indices. Models adjusted for age, sex, and body mass index. PHQ-9: Patient Health Questionnaire-9.
Figure 4.
↓  Figure 5. Subgroup-specific odds for PHQ-9–based depression comparing lowest vs. highest UPF intake quartiles. HS: high school level education; PHQ-9: Patient Health Questionnaire-9.
Figure 5.
↓  Figure 6. Subgroup-specific Odds for PHQ-9–based depression comparing lowest vs. highest water intake quartiles. HS: high school level education; PHQ-9: Patient Health Questionnaire-9.
Figure 6.
↓  Figure 7. Independent and interactive effects of ultra-processed food and water intake on PHQ-9–based depression. Models adjusted for age, sex, and body mass index. PHQ-9: Patient Health Questionnaire-9.
Figure 7.

Tables

↓  Table 1. Baseline Characteristics of All Participants
 
Variable Participants (n = 4,248)
BMI: body mass index; CI: confidence interval; n: number of subjects; PHQ-9: Patient Health Questionnaire-9; UPF: ultra-processed food.
Age (years), mean (CI) 50.8 (50.2–51.5)
Cigarette smoking, % (CI) 14.1 (11.9–16.3)
Alcohol drinking, % (CI) 18.5 (16.6–20.3)
Gender (males), % (CI) 43.8 (42.4–45.4)
BMI (kg/m2), mean (CI) 30.1 (29.8–30.5)
PHQ-9 score, mean (CI) 3.61 (3.50–3.73)
PHQ-9–based depression prevalence, % (CI) 10.9 (10.0–11.8)
UPF intake: % daily calories from added sugar, mean (CI) 4.81 (4.74–4.88)
Water intake (g/day), mean (CI) 2,743 (2,652–2,835)

 

↓  Table 2. Quartile Based Frequencies of UPF and Water Intake
 
UPF quartile Unweighted frequency (n, %) Weighted frequency (n, %) Water quartile Unweighted frequency (n, %) Weighted frequency (n, %)
n: number of subjects; UPF: ultra-processed food.
1 1,134 (26.4) 36,144,482 (27.9) 1 966 (22.5) 26,910,211 (20.7)
2 1,079 (25.1) 32,235,216 (24.9) 2 1,063 (24.7) 30,063,451 (23.2)
3 1,069 (24.9) 31,326,899 (24.2) 3 1,061 (24.7) 33,138,565 (25.5)
4 1,014 (23.6) 29,974,104 (23.1) 4 1,210 (28.1) 39,731,508 (30.6)
Total 4,296 129,680,701 (100) Total 4,300 129,843,735 (100)

 

↓  Table 3. Prevalence of PHQ-9–Based Depression by UPF and Water Intake
 
UPF quartile Depression (%) Water quartile Depression (%)
PHQ-9: Patient Health Questionnaire-9; UPF: ultra-processed food.
1 10.7 1 15.4
2 8.7 2 9.0
3 10.7 3 10.2
4 15.4 4 10.9

 

↓  Table 4. Survey-Weighted Linear Regression of Continuous Predictors of Log-Transformed PHQ-9 Depression Score
 
Predictor β estimate t value P value
aStandardized β = +0.19 in sensitivity model. bRounded to 0.00 from SPSS output. BMI: body mass index; PHQ-9: Patient Health Questionnaire-9; UPF: ultra-processed food.
UPF intake +0.17a 4.51 < 0.0001
Water intake (g/day) 0.00b –3.23 0.0012
Age (years) –0.04 –9.39 < 0.0001
Male (sex) –0.79 –5.00 < 0.0001
BMI (kg/m2) +0.05 3.98 < 0.0001
UPF × water intake interaction –0.07 –2.38 0.017

 

↓  Table 5. Sensitivity Analysis: UPF Quartiles and Depression Adjusted for Smoking and Drinking Alcohol
 
Variable P-value OR (Exp(B)) 95% CI
BMI: body mass index; CI: confidence interval; OR: odds ratio; UPF: ultra-processed food.
Age < 0.001 0.978 0.978–0.978
Male (vs. female) < 0.001 0.618 0.617–0.619
BMI < 0.001 1.021 1.020–1.021
Drinking alcohol vs. no alcohol < 0.001 0.640 0.638–0.641
Smoking status
  Never vs. current < 0.001 2.365 2.361–2.369
  Never vs. former < 0.001 1.257 1.255–1.259
UPF quartile
  Q2 vs. Q1 < 0.001 0.926 0.925–0.928
  Q3 vs. Q1 < 0.001 1.115 1.113–1.117
  Q4 vs. Q1 < 0.001 1.493 1.491–1.495

 

↓  Table 6. Sensitivity Analysis: Water Intake Quartiles and Depression Adjusted for Smoking and Drinking Alcohol
 
Variable P-value OR (Exp(B)) 95% CI
BMI: body mass index; CI: confidence interval; OR: odds ratio; UPF: ultra-processed food.
Age < 0.001 0.976 0.976–0.976
Male (vs. female) < 0.001 0.620 0.619–0.620
BMI < 0.001 1.020 1.020–1.020
Drinking alcohol vs. no alcohol < 0.001 0.664 0.663–0.665
Smoking status
  Never vs. current < 0.001 2.161 2.157–2.164
  Never vs. former < 0.001 1.256 1.254–1.258
UPF quartile
  Q2 vs. Q1 < 0.001 0.911 0.910–0.913
  Q3 vs. Q1 < 0.001 1.065 1.063–1.067
  Q4 vs. Q1 < 0.001 1.346 1.344–1.348
Water quartile
  Q2 vs. Q1 < 0.001 0.608 0.607–0.609
  Q3 vs. Q1 < 0.001 0.527 0.526–0.527
  Q4 vs. Q1 < 0.001 0.526 0.525–0.527

 

↓  Table 7. Sensitivity Analysis: Joint UPF and Water Model Adjusted for Smoking and Drinking Alcohol
 
Variable P-value OR (Exp(B)) 95% CI
BMI: body mass index; CI: confidence interval; OR: odds ratio; UPF: ultra-processed food.
Age < 0.001 0.976 0.976–0.976
Male (vs. female) < 0.001 0.619 0.618–0.620
BMI < 0.001 1.020 1.020–1.020
Drinker (vs. non-drinker) < 0.001 0.663 0.662–0.664
Smoking status
  Never vs. current < 0.001 2.174 2.171–2.177
  Never vs. former < 0.001 1.257 1.255–1.258
UPF quartile
  Q2 vs. Q1 < 0.001 0.828 0.826–0.829
  Q3 vs. Q1 < 0.001 0.888 0.886–0.891
  Q4 vs. Q1 < 0.001 1.043 1.040–1.047
Water quartile
  Q2 vs. Q1 < 0.001 0.553 0.552–0.554
  Q3 vs. Q1 < 0.001 0.439 0.438–0.440
  Q4 vs. Q1 < 0.001 0.407 0.406–0.409
UPF × water interaction < 0.001 1.034 1.034–1.035