Introduction

The prevalence of mental illnesses is growing as a global issue1. Anxiety and depressive disorders are the most common, including in lower resourced countries2, often co-occurring and significantly impairing an individual’s quality of life and well-being3. In the 2020 Nepal national mental health survey the prevalence of major depressive disorder (MDD) among adults was 2.9% and generalized anxiety disorder (GAD) was 0.8%4. Thirty percent of mothers reported having symptoms of postpartum depression in Kathmandu, Nepal5, and among women with children under 5 years in rural Nepal, 41.5% had moderate-to-severe depression symptoms and 34% had anxiety symptoms6.

Various recent reviews have shown the importance of diet on mental health, emphasizing the relevance of modifiable life styles factors in reducing depression and anxiety. For example, high fruit and vegetables intake was associated with less anxiety7, less depressive symptoms8,9 and less clinical depression10. Fiber intake was found to reduce anxiety and depressive outcomes11 and avoiding meat consumption was associated with increased depression and anxiety12. More precisely, these investigations have examined the connection between specific nutrients and mental health13. A diverse diet is the foundation of an adequate and balanced supply of nutrients, regardless of the importance of individual nutrients14.

In a recent review15 on dietary diversity and health outcomes, only two studies evaluated the relationship between dietary diversity and mental health among the general adult population, showing an inverse association between dietary diversity and depressive symptoms in Iran16, and anxiety symptoms in Iran17. Moreover, among American knowledge workers low levels of dietary diversity were associated with depressive symptoms18. Low dietary diversity (≤ five food groups) was linked to almost twice as many cases of depression in Bangladeshi women of reproductive age, while eating dairy, eggs, fish, and foods high in vitamins A and C was linked to a lower risk of depression19. Previous studies16,17,18,19 investigated dietary diversity only in relation to one mental health outcome (either depressive or anxiety symptoms), yet it is unclear whether dietary diversity is associated with two mental health outcomes (anxiety and depression). No study to date has examined the association of dietary diversity with GAD and/or MDD among Nepalese women of reproductive age. There is a high prevalence of depression and/or anxiety among women of reproductive age in Nepal (e.g., 41.5% had moderate-to-severe depression symptoms, and 34% had anxiety symptoms20, and 30% had post-partum depressive symptoms5), which warrants its study. Thus, using information from the Nepal Demographic and Health Survey (NDHS) for 2022, the purpose of the current study was to investigate the relationship between the dietary diversity score and symptoms of depression and generalized anxiety in women in Nepal who are of reproductive age.

Method

Setting

Nepal with a lower-middle income South Asian economy has a population of over 30 million, concentrated in the Tarai or low land region and the hilly region; overall density is quite low, with a rapid urbanization rate of 23% in 2014 to 66% in 2017. By religion, most (81.2%) are Hindu, 8.2% Buddhist, and 5.1% Muslim. The literacy rate among women is 63.3% and 32.8% of women are married by age 1821,22.

Sample and procedure

The sample was restricted to those female participants who responded to the mental health questionnaire in the 2022 NDHS. Using a multi-stage sampling design, a nationally representative household-based sample was included. The response rate for the women’ interview sample was 97%23. All women aged 15–49 who were either long-term residents of the chosen homes or guests who spent the night before the survey were questioned by the survey interviewers23. The 2022 NDHS was approved by the “Nepal Health Research Council (NHRC) and the ICF Institutional Review Board,” and written informed consent was obtained from the household head to conduct interviews. All methods were carried out in accordance with relevant guidelines and regulations and have been performed in accordance with the Declaration of Helsinki.

Measures

Exposure variable

Dietary measures: Women's Dietary Diversity Score (WDDS-10)

In a 24 h food consumption recall 10 food groups were assessed:

(1) Grains (white/pale starchy roots, tubers, and plantains), (2) Pulses (beans, peas, and lentils), (3) Nuts and seeds, (4) Dairy (milk, cheese, yogurt, other milk products), (5) Flesh foods (meat, fish, poultry and liver/organ meats), (6) Eggs, (7) Dark green leafy vegetables, (8) Vitamin A rich fruits and vegetables, (9) Other vegetables and (10) Other fruits (scores 0–10)23,24.

Among women of reproductive age, the WDDS-10's minimum food group consumption threshold of five out of the ten food groups is a reliable indicator of adequate dietary micronutrient intake25.

Outcome variables

The 9-item Patient Health Questionnaire (PHQ-9) on common symptoms of depression in the previous two weeks were used to assess MDD symptoms26. The scale for rating responses ranged from 0 for "not at all" to 3 for "always." A validated Nepali cutoff score of 0–4 for no depression, 5–9 for mild depression, and 10 or higher for moderate-to-severe depression (sensitivity = 0.94, specificity = 0.80) was used to determine the responses27. In this sample, the PHQ-9's Cronbach alpha was 0.84.

The seven-item (GAD-7) scale was used to measure GAD symptoms; a score of 0–4 indicated no anxiety, a score of 5–9 indicated mild anxiety, and a score of 10 or higher indicated moderate-to-severe GAD28. In this sample, the GAD-7's Cronbach alpha was 0.86.

Covariates23

Sociodemographic factors assessed included age, marital status (married, cohabiting, never married, widowed, divorced, and separated), education (no education, and ≥ 1 years of education), wealth status, religion (Hindu, Buddhist, Muslim, Other), residence status (rural and urban), region (Terai or lowland region, Mountain, and Hill region), and health insurance coverage.

Current tobacco use was assessed from 2 items, “Frequency smokes cigarettes” and “Frequency currently uses other type of tobacco”.

Current alcohol use was assessed from the item, “We count one drink of alcohol as one can or bottle of beer, one glass of wine, one shot of spirits, or one cup of jaand, chyang. During the last one month, on how many days did you have at least one drink of alcohol?”.

Pregnancy losses were sourced from the question “How many miscarriages, abortions, and stillbirths have you had?”.

Sons and/or daughters who had died was measured from the questions, “Sons who have died” and “Daughters who have died”.

Data analysis

Student t-test was used to calculate differences in means. Multinominal logistic regression was applied to estimate the associations between dietary diversity and mild and moderate-to-severe MDD and mild and moderate-to-severe GAD anxiety symptoms (with no depressive or no anxiety symptoms as reference category), separately. The second model was adjusted for age, education, wealth status, religion, place of residence, region, and marital status while the first model was unadjusted. Model 3 was further adjusted for health insurance, tobacco use, alcohol use, pregnancy loss and sons and/or daughters died. Additionally, associations between specific food groups and moderate-to-severe depressive and moderate-to-severe generalized anxiety symptoms were estimated using binary logistic regression. Age, education, wealth status, religion, place of residence, marital status, health insurance, alcohol and tobacco use, pregnancy loss, and the death of sons or daughters were all taken into account when creating this model.

Covariates were included based on literature review, including age, education, marital status, income16,17, residence status29, live birth, still birth19, religion19,30, health insurance30, region31, and substance use29. p significance was set at < 0.05. Collinearity was checked with Variance Inflation Factor (VIF), but none was found. Version 15.0 of the STATA software (Stata Corporation, College Station, TX, USA) was used for all statistical procedures, taking the complex study design into account.

Ethical approval

The 2022 NDHS was approved by the “Nepal Health Research Council (NHRC) and the ICF Institutional Review Board,” and written informed consent was obtained from the household head to conduct interviews. All methods were carried out in accordance with relevant guidelines and regulations and have been performed in accordance with the Declaration of Helsinki.

Results

In all, 7442 women with mental health module measurements were included in the sample of women (15–49 years old). The distribution of the dietary diversity score and the sample characteristics are shown in Table 1. Most women (74.7%) were married or cohabiting, 26.8% had no education, and 36.6% had a poor or poorest wealth status. By religion, most (83.0%) were Hindu, lived in urban areas (68.3%) and in the Terai or lowland region (55.4%). More than one in ten (12.2%) of the women had a health insurance, 7.5% were current tobacco users, 10.8% current alcohol users, 18.5% reported pregnancy loss and 9.4% sons and/or daughters died.

Table 1 Sample characteristics of women in reproductive age, Nepal, 2022.
Full size table

The prevalence of mild and moderate-to-severe MDD was 15.7% and 5.4%, respectively, and the prevalence of mild and moderate-to-severe GAD was 20.8% and 7.5%, respectively. The overall dietary diversity mean score was 4.66 (SD = 1.67). The dietary diversity score differed significantly by age group, education, wealth status, religion, residence status, region, health insurance coverage, tobacco use and sons and/or daughters died (see Table 1).

Associations with major depressive disorder and generalized anxiety symptoms

In the crude multinomial regression model, dietary diversity was inversely associated with mild and moderate-to-severe MDD symptoms and GAD symptoms, and in Model 3, adjusted for relevant confounders, dietary diversity was inversely associated with moderate-to-severe MDD symptoms (Adjusted Incidence Risk Ratios-AIRR: 0.90, 95% CI 0.84–0.97), and with moderate-to-severe GAD symptoms (AIRR: 0.86, 95% CI 0.80–0.92) (see Table 2).

Table 2 Associations between dietary diversity score and depressive symptoms and generalized anxiety symptoms (with no depressive and no generalized anxiety symptoms as reference category).
Full size table

Associations between food groups and major depressive disorder and generalized anxiety symptoms

In the fully adjusted regression model, pulses (Adjusted Odds Ratio-AOR: 0.77, 95% CI 0.60–0.98) and Vitamin A rich fruits and vegetables (AOR: 0.69, 95% CI 0.51–0.94) were inversely associated with MDD symptoms. Furthermore, Vitamin A rich fruits and vegetables (AOR: 0.57, 95% CI 0.43–0.75), dairy (AOR: 0.80, 95% CI 0.67–0.97), and pulses (AOR: 0.69, 95% CI 0.56–0.85) were inversely associated with GAD symptoms (see Table 3).

Table 3 Dietary diversity by food groups and depression symptoms and generalized anxiety symptoms.
Full size table

The distribution of the ten food groups' intake by low and high dietary diversity scores is shown in Table 4. When comparing the high dietary diversity group to the low diversity group, the high diversity group consumed more of each particular food group. The highest proportion of a food group intake in the high diversity group was found for grains (100%), other vegetables (88.7%), followed by pulses (87.9%), dairy (73.6%), and dark green leafy vegetables (67.1%), and was lowest for nuts and seeds (24.7%), followed by eggs (26.0%), and vitamin A rich fruits and vegetables (33.3%) (see Table 4).

Table 4 Food group consumption by low and high dietary diversity score.
Full size table

Discussion

The study aimed to assess the association between the dietary diversity score, and depressive and generalized anxiety symptoms in women of reproductive age in Nepal. The main finding was that dietary diversity was inversely and significantly associated with MDD and GAD symptoms, and in addition, Vitamin A fruit and vegetables and pulses intake decreased the odds of MDD and GAD symptoms. These associations persisted after adjustment for a number of relevant confounders.

Consistent with previous research15,16,17,19, this study found an inverse association between the dietary diversity score, and depressive and generalized anxiety symptoms in women of reproductive age in Nepal. Overall, the inverse odds ratios of dietary diversity seem to have been lower with anxiety than with depressive symptoms, suggesting a larger impact of dietary diversity on anxiety than depressive symptoms. It has been proposed in dietary diversity guidelines that higher dietary diversity may lead to better physical health by increasing the intake of adequate micronutrients, and more likely increase the intake of healthy food groups15,32. Increasing dietary diversity may increase healthier microbiota, reduce oxidative stress, and increase immune response, which can be beneficial for mental health32.

Regarding specific food groups, the study found in consistence with previous reviews8,9,11 that Vitamin A rich fruit and vegetable and fiber intake were inversely associated with anxiety and depressive symptoms. In a study among perinatal women in Bangladesh, the depression lowering food groups included eggs, fish, and vitamin C-rich foods, while vitamin A-rich foods showed almost no association19. The mechanism of how fruit and vegetable intake can improve psychological well-being is not yet clear9,33. One possible explanation is that fruit and vegetable antioxidants can help lower inflammatory markers, which have been connected to the emergence of mental health conditions like depression33,34. Potentially shared mechanisms between fiber consumption and mental health include changes in the composition of the intestinal microbiome and a reduction in oxidative stress35.

The high dietary diversity group consumed more of each particular food group than the low diversity group, according to the study's findings. Similar results were found in previous studies17. The found prevalence of mild (15.7%) and moderate-to-severe (5.4%) MDD symptoms, and the prevalence of mild (20.8%) and moderate-to-severe (7.5%) GAD symptoms were lower than in local studies among women of reproductive age in Nepal (41.5% moderate-to-severe depression symptoms, 34% anxiety symptoms20, and 30% post-partum depressive symptoms5), but were higher than in a study among adult women in the region, in Bhutan (15.4% and 2.9% for mild and moderate/severe MDD, and 9.7% and 2.0% for mild and moderate/severe GAD, respectively)36.

Study strength and limitations

A sizable nationally representative population sample of women of reproductive age was used by the 2022 NDHS, and standardized DHS measures, e.g., on dietary and mental health assessment. Study limitations include the cross-sectional study design, which hinders us to draw causative conclusions, and self-report of the data. Further, the 2022 NDHS did not assess social support and physical activity, which could have an influence on mental health16,17. Although body mass index and anemia status were assessed in the 2022 NDHS, the sample with the mental health module did not include body mass index and anemia status. Future studies should include social support, physical activity, body mass index and anemia status 16,17.

Conclusion

Dietary diversity was inversely associated with MDD and GAD symptoms, although reverse causality cannot be ruled out as explanation. It is suggested to increase dietary diversity by eating a wide variety of foods. In addition, fruit and vegetable and pulses intake decreased the odds of MDD and GAD showing the importance of these two food groups to promote mental health. Longitudinal studies are needed to confirm findings.