Research paperFruit and vegetable intake in relation to depressive and anxiety symptoms among adolescents in 25 low- and middle-income countries
Introduction
Mental disorders account for approximately 14% of the global burden of disease, with depression and anxiety serving as the leading causes of disability worldwide (Murray et al., 2012; Whiteford et al., 2013). More than 80% of people with mental disorders live in low- and middle-income countries (LMICs) (World Health Organization (WHO), n.d.), making the study of mental health and related issues in LMICs especially relevant. The onset of these conditions typically occurs in adolescence (Kessler et al., 2007) which is accompanied by subsequent risk of social and cognitive impairment (Castaneda et al., 2008), engaging in unhealthy lifestyle behaviors (Skrove et al., 2013), and having a higher risk of early-onset cardiovascular disease (Gross et al., 2018) and suicide (Franklin et al., 2017). Further, depression affects an estimated 350 million people globally (Organization, 2011), and is the most common mental disorder among adolescents (Merikangas et al., 2009). A recent meta-analysis identified the pooled prevalence of depressive and anxiety disorder among children at 2.6% and 6.5%, respectively (Polanczyk et al., 2015). Mental disorders place a substantial burden on individuals and their families; with evidence suggesting that having a mental disorder decreases the likelihood of completing school, getting a full-time job and having a higher quality of life (Doran and Kinchin, 2019). Therefore, prevention of mental disorders is imperative to help decrease their burden on individual's health, society, and economies.
Diet plays a major role in the prevention of chronic non-communicable diseases (Fardet and Boirie, 2014), such as cardiovascular diseases and diabetes (Mozaffarian, 2016); and it has been argued that dietary factors may play an important role in the prevention of depression (Sanchez-Villegas and Martínez-González, 2013). For example, consumption of fruit and vegetables, which are rich in antioxidants and anti-inflammatory components, has been shown to exert a protective effect against depression (Liu et al., 2016; Saghafian et al., 2018). However, evidence on the relationship between fruit and vegetable intake (FVI) and anxiety is insufficient and yields inconsistent results (Khalid et al., 2016; Saghafian et al., 2018). Much of the existing research focuses on adults (Liu et al., 2016; Saghafian et al., 2018), while little is known about adolescents (Khalid et al., 2016) for whom preventative strategies may differ from those aimed at adults. In addition, despite a high mental disorder burden in LMIC (Yatham et al., 2017), there is, largely, a lack of evidence on the association of FVI with depression and anxiety in adolescents living in these countries (Liu et al., 2016; Saghafian et al., 2018). Evidence obtained in high-income countries (HICs) may not be readily translatable considering that LMICs have social, cultural, and economic characteristics that differ from those of HICs (Yatham et al., 2017). Therefore, the objective of our study was to explore the association of FVI with depressive and anxiety symptoms among adolescents living in 25 LMICs.
Section snippets
Study population
Data were obtained from the Global School-based Health Survey (GSHS), a collaborative surveillance project coordinated by the World Health Organization and the United States Centers for Disease Control and Prevention (CDC). The GSHS aimed to assess and quantify behavioral risk and protective factors among students. Details about the study design and sampling strategy are available elsewhere (CDC, n.d.). Briefly, a standardized two-stage cluster sampling process was conducted to select
Results
Table 1 displays the characteristics of the weighted population by country and region. Among 65267 adolescents aged 12–15 years, the pooled estimates of overall prevalence rates were 30.3% (95% confidence interval (CI) = 27.0–33.8) for depressive symptoms and 8.3% (95% CI = 7.9–11.9) for anxiety symptoms. FVI of <5 times/d (lack of adequate intake) was observed in 85.3% of the participants (ranging from 71.4% in Seychelles to 95.2% in Argentina). The pooled prevalence of no fruit intake and
Discussion
In this multi-national study of adolescents, inadequate vs. adequate FVI was associated with a higher risk of depressive symptoms but not anxiety symptoms after combining effect sizes from 25 LMICs. When examined separately, fruit intake was significantly associated with both lower risks of depressive and anxiety symptoms; while vegetable intake was associated with a lower risk of depressive symptoms, but not with anxiety symptoms (only becoming significant after additionally adjusted for BMI
Limitations
This study has several strengths, including the large sample size, the multi-national scope, the focus on adolescents in LMICs, and investigating FVI in relation to anxiety, much of which are critical yet rarely investigated. However, there are several limitations. First, due to the cross-sectional design of the study, no conclusion about causality can be drawn. Second, GSHS exclusively surveyed adolescents in schools. Therefore, the results cannot be generalized to those who have no access to
Conclusion
Our study provides multi-national evidence of the protective effect of FVI against depressive and anxiety symptoms among adolescents in LMICs. This was independent of physical activity, being bullied, smoking status, and alcohol intake. The associations between vegetable intake and depressive/anxiety symptoms were significant among females but not among males. However, the association between FVI and anxiety is inconclusive and requires further research. This work can inform policymakers in
Contributors
Mr Liu and Prof He conceived and designed the study and had primary responsibility for the final content. Mr Liu contributed to the data analysis, overseen by Mr Zhang, Yu, and, Tang. Mr Liu, Drs Chen, and Prof Towne drafted the manuscript. Mr Liu, Prof Towne, and Gasevic contributed to critical revision of the manuscript. All authors contributed to the conception, design, and interpretation of the data. All authors approved the final manuscript as submitted and agree to be accountable for all
CRediT authorship contribution statement
Ming-wei Liu: Conceptualization, Data curation. Qiu-tong Chen: Conceptualization, Data curation. Samuel D. Towne: Conceptualization, Data curation. Jie Zhang: Conceptualization, Data curation. Hong-jie Yu: Conceptualization, Data curation. Rui Tang: Conceptualization, Data curation. Danijela Gasevic: Conceptualization, Data curation. Pei-gang Wang: Conceptualization, Data curation. Qi-qiang He: Conceptualization, Data curation.
Declaration of Competing Interest
None.
Acknowledgments
We thank the World Health Organization and the United States Centers for Disease Control and Prevention.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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2020, Journal of Affective DisordersCitation Excerpt :Second, there was no information on disability, despite the fact that it may play an important role in the association between physical injury and depression. Third, although the question on depressive symptoms used in our study has been used in a multitude of previous studies using the same dataset (Balogun et al., 2014; Liu et al., 2020; Vancampfort et al., 2018), while it referred to core symptoms of depression, the fact that depressive symptoms were assessed with a single question, and the lack of validity studies for this particular question are limitations of this study. Future studies with validated measures or clinical assessment of depressive symptoms/depression are warranted.