J Clin Med Res

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

Journal website https://jocmr.elmerjournals.com

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

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 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 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 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 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 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.

**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 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 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.

1,134 (26.4)

36,144,482 (27.9)

966 (22.5)

26,910,211 (20.7)

1,079 (25.1)

32,235,216 (24.9)

1,063 (24.7)

30,063,451 (23.2)

1,069 (24.9)

31,326,899 (24.2)

1,061 (24.7)

33,138,565 (25.5)

1,014 (23.6)

29,974,104 (23.1)

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 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.

10.7

15.4

8.7

9.0

10.7

10.2

15.4

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	+0.17^a	4.51	< 0.0001
Water intake (g/day)	0.00^b	–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 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

+0.17^a

4.51

< 0.0001

Water intake (g/day)

0.00^b

–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 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 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

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