Mediterranean diet-based intervention to improve depressive symptoms: analysis of the PREDIDEP randomized trial

Figures & data

Figure 1. Flowchart of participant screening, recruitment, and randomization.

Table 1. Baseline characteristics of PREDIDEP participants.

Characteristics	Control (n = 93)	Intervention (n = 103)	p-value*
Age, years, mean (SD)	51.48 (14.7)	51.16 (13.79)	0.8647
Sex, n (%)			0.588
Men	23 (24.73)	29 (28.16)
Women	70 (75.27)	74 (71.84)
Depressive episodes, n (%)
1	42 (45.16)	35 (33.98)	0.274
2	21 (22.58)	27 (26.21)
3 or more	30 (32.26)	41 (39.81)
Antidepressants use, n (%)	70 (75.27)	81 (78.64)	0.575
Civil status, n (%)			0.558
Single	33 (35.87)	34 (33.01)
Married	37 (40.22)	49 (47.57)
Others	22 (23.91)	20 (19.41)
Education, n (%)			0.613
Secondary or less	48 (52.17)	50 (48.54)
University	44 (47.82)	53 (51.45)
Working status, n (%)
Working	39 (42.39)	47 (45.63)	0.826
Retired	16 (17.39)	19 (18.45)
Others	37 (40.22)	37 (35.92)
BMI (kg/m^2)	26.04 (5.29)	26.09 (4.78)	0.945
Smoking status, n (%)	24.00 (26.09)	24.00 (23.30)	0.457
Illegal drugs, n (%)	8.00 (8.6)	9.00 (8.74)	0.973
Depressive symptoms (BDI)	5.78 (5.24)	6.41 (5.84)	0.428
Physical activity (MET-hours/week)	16.30 (19.19)	18.13 (24.99)	0.5694
MEDAS score (14 items)	7.01 (2.1)	7.04 (1.97)	0.8959
HRQoL scores (SF-36)
MSC	37.07 (7.13)	37.85 (7.00)	0.4462
PSC	47.81 (7.35)	48.36 (7.21)	0.6002
Energy intake (kcal/day)	2531.00 (809)	2683.00 (874)	0.2094

*p-value obtained by the Student’s t test (quantitative variables) or the Chi-square (qualitative variables).

BDI: Beck Depression Inventory; BMI: body mass index; HRQoL: Health Related Quality of Life; MET: Metabolic equivalent; MEDAS: Mediterranean Diet Adherence Screener; MSC: Mental Summary Component; PSC: Physical Summary Component.

Table 2. Effect of an intervention based on Mediterranean diet enriched with EVOO on changes in depressive symptoms in PREDIDEP study.

	Control group, mean change (CI 95%)		Intervention group, mean change (CI 95%)		Control vs. Intervención
					Between-group difference
Depressive symptoms	Intention-to-treat^a (n = 93)	Completers-only^b (n = 39)	Intention-to-treat^a (n = 103)	Completers-only^b (n = 52)	Intention-to-treat^a (MI)	p-value^c	Completers-only^b	P-value^c
4-months change	0.94 (−0.97–2.86)	1.11 (−0.86–3.08)	−2.15 (−4.00 to −0.29)	−2.17 (−3.72 to −0.62)	−3.10 (−5.72 to −0.47)	0.021	−3.28 (−5.79 to −0.77)	0.010
8-months change	−0.30 (−2.13–1.53)	−0.21 (−1.68–1.27)	−2.42 (−4.17 to −0.67)	−2.50 (−3.96 to −1.04)	−2.12 (−4.67–0.42)	0.102	−2.29 (−4.37 to −0.22)	0.030
16-months change	0.31 (−1.71–2.34)	0.55 (−1.13–2.23)	−0.21 (−2.12–1.70)	−0.07 (−2.19–2.06)	−0.52 (−3.44–2.39)	0.723	−0.61 (−3.33–2.10)	0.657
20-months change	1.83 (−0.13–3.80)	1.74 (−0.19–3.68)	−1.51 (−3.37–0.35)	−1.18 (−2.81–0.46)	−3.35 (−6.08 to −0.61)	0.017	−2.92 (−5.45 to −0.39)	0.024
24-months change	−0.66 (−2.59–1.26)	−0.17 (−1.71–1.38)	−1.78 (−3.63–0.70)	−1.17 (−2.95–0.61)	−1.12 (−3.73–1.50)	0.403	−1.00 (−3.36–1.36)	0.405

Note: CI: Confidence Interval. BDI: Beck Depression Inventory.

^a Calculated using mixed-effect models with multiple imputation method with 20 imputations for each missing measurement.

^b Calculated using mixed-effect models.

^c p-value between group intervention difference.

Table 3. The effects of dietary intervention on depressive symptoms changes at every independent temporal evaluation in completers-only participants in PREDIDEP study.

Depressive symptoms	n	Control group, mean change (CI 95%)	Intervention group, mean change (CI 95%)	Between-group difference (CI 95%)	p-value^a
4-months change	161	0.91 (−1.09–2.90)	−2.14 (−3.71 to −0.58)	−3.05 (−5.59 to −0.51)	0.018
8-months change	169	−0.38 (−1.85–1.09)	−2.62 (−4.11 to −1.13)	−2.24 (−4.33 to −0.14)	0.036
16-months change	147	0.25 (−1.47–1.97)	−0.55 (−2.69–1.60)	−0.80 (−3.55–1.95)	0.570
20-months change	132	1.66 (−0.32–3.64)	−1.91 (−3.52 to −0.30)	−3.57 (−6.12 to −1.01)	0.006
24-months change	132	−0.39 (−1.89–1.12)	−1.86 (−3.65 to −0.09)	−1.48 (−3.81–0.86)	0.215

Note: CI: Confidence Interval. BDI: Beck Depression Inventory.

Calculated using mixed-effect models.

^a p-value between group intervention difference.

Table 4. Mean changes in depressive symptoms after 4 and 8 months of follow-up according to baseline Mediterranean Diet adherence in the PREDIDEP study (n = 151).

Depressive symptoms	Low adherence to MD (MEDAS≤9), mean change (CI 95%) (n = 118)	High adherence to MD (MEDAS>9), mean change (CI 95%) (n = 33)	Between-group difference (CI 95%)	p-value^a
4-months change	−0.81 (−2.25–0.62)	−0.86 (−3.42–1.70)	−0.04 (−2.98–2.89)	0.976
8-months change	−1.25 (−2.49–0.001)	−2.06 (−4.05 to −0.08)	−0.82 (−3.16–1.52)	0.493

Note: CI: Confidence Interval. BDI: Beck Depression Inventory. MD: Mediterranean Diet; MEDAS: Mediterranean Diet Adherence Screener.

Calculated using mixed-effect models.

p-value between group intervention difference.

Adjusted for intervention group, age, sex, working status, smoking habit, BMI and civil status.

Table 5. Mean change and 95% confidence interval in depressive symptoms after 16, 20, and 24 months of follow-up according to annual change in the adherence to the Mediterranean Diet in the PREDIDEP study (n = 95).

Depressive symptoms (BDI)	Low maintained adherence (95% CI) (n = 41)	Increased adherence (95% CI) (n = 33)	Decreased adherence (95% CI) (n = 5)	High maintained adherence (95% CI) (n = 16)	p-value^a
16-months change	1.11 (−1.04–3.27)	−1.10 (−3.98–1.77)	−2.23 (−4.06 to −0.40)	0.44 (−3.17–4.04)	0.267
20-months change	0.62 (−1.20–2.74)	0.11 (−2.26–2.47)	−1.26 (−3.38–0.85)	−1.02 (−4.07–2.03)	0.764
24-months change	−0.22 (−1.81–1.36)	−0.21 (−2.81–2.39)	−0.66 (−2.81–1.49)	−4.67 (−7.18 to −2.17)	0.697

Note: CI: Confidence Interval. BDI: Beck Depression Inventory; MEDAS: Mediterranean Diet Adherence Screener.

Calculated using mixed-effect models.

^a p-value between group intervention difference.

Adjusted for intervention age, sex, and smoking habit.

Data availability statement

The data that support the findings of this study are available from the corresponding author [ASV], upon reasonable request.

Trial registration number: ClinicalTrials.gov NCT03081065.