Review
Could pesticide exposure be implicated in the high incidence rates of depression, anxiety and suicide in farmers? A systematic review

https://doi.org/10.1016/j.envpol.2023.121888Get rights and content

Highlights

  • Farming and pesticide exposure are risk factors for depression.

  • Pesticide poisoning is a risk factor for suicidal behavior.

  • Depression and suicide outcomes are more common in pesticide-exposed males than females.

  • Older farmers are more likely to be depressed or to commit suicide.

  • Restricting pesticide access may be a protective strategy to reduce suicide attempts.

Abstract

Pesticide exposure and poisoning may rise the risk of mental health problems and suicidal tendencies. To explore the potential connection between chronic occupational exposure to pesticides and depression, anxiety, and suicide-related outcomes in farmers, a systematic review was performed. Systematic review protocol is available in PROSPERO registration number CRD42022316285. A total of fifty-seven studies met inclusion criteria: twenty-nine on depression or other mental disorders, twelve on suicide (two of them on both depression and suicide), and fourteen on pesticide poisoning or self-poisoning and death. Among the fifty-seven selected studies, eighteen were conducted in Asia, seventeen in North America, fourteen in South America, seven in European Union, one in Africa, and one in Australia/Oceania. Selected studies demonstrated an increased prevalence of depressive disorders in farmworkers exposed to pesticides as well as an increased self-reported prevalence of depression in this population. Moreover, previous pesticide poisoning increased the risk estimates for depression or other mental disorders as compared with chronic pesticide exposure. Severe pesticide poisoning and multiple poisoning showed increased risks of depressive symptoms compared with milder cases. In addition, financial difficulties and poor health were positively correlated with depression. Among studies on suicide, nine of them found that suicide rates increased in areas devoted to agriculture with intensive pesticide consumption. Moreover, studies demonstrate a higher suicide risk among farmers. The present review suggests more attention to the farmer's mental health and more detailed studies on occupational exposure to the mixture of these compounds.

Introduction

Mental health conditions are risk factors for a range of illnesses and contribute to poor health outcomes and national economic loss, according to World Health Organization (WHO), which implemented the Special Initiative for Mental Health 2019–2023 aiming to provide universal and quality access to interventions and special care for individuals with mental disorders (WHO, 2019a).

Worldwide, depressive disorders represent the third-leading cause of the burden of disease, affecting around 322 million people around the globe. (WHO, 2017). Considering that depression is associated with poor health outcomes, understanding what factors may give rise to depression and anxiety is important to have an effective health policy, planning, and evaluation, as well as scale-up quality interventions and services for people with depression.

The connection between pesticide exposure and mental health conditions has been investigated by several studies, such as those included in this systematic review. Studies have shown that farmers, which are occupationally exposed to pesticides, are more susceptible to anxiety and depression (Sanne et al., 2003; Meyer et al., 2010; Beard et al., 2014). Moreover, the study by Ringgenberg et al. (2018) showed increased suicide rate among farmers as compared with general. The mechanisms underlying such epidemiological associations are unknown; however, some studies addressed the involvement of genetic factors, oxidative damage, and alterations in neurotransmitter systems in pesticide effects (Savy et al., 2018; Martínez et al., 2018; Cattani et al., 2017; Cattani et al., 2021). In addition to occupational exposure to pesticides, social isolation, less educational attainment, and financial stress are suggested as causes of depression in agricultural areas (Beseler and Stallones, 2008; Hong et al., 2009).

The impacts of the pesticide exposure to farmer's mental health outcomes, especially in affective disorders, were not fully understood. Our research group is committed to understanding the harmful impacts of pesticides and other toxic compounds on human and environmental health. Using a pre-clinical animal model, we demonstrated that the poisonous effects of perinatal exposure to glyphosate on the central nervous system account for depressive-like behavior in male adult offspring (Cattani et al., 2014; Cattani et al., 2017), suggesting that neurodevelopmental exposure to the pesticide may impact mental health later in life. These results reinforce that the neurodevelopmental impacts of glyphosate, the major pesticide used in Brazil and around the globe, may account for long-term brain damage.

The knowledge about the harmful impacts of pesticide exposure on mental health is particularly relevant. Previously, in 2013, Freire and Koifman conducted a systematic review including 25 studies providing evidence of a probable connection between pesticide exposure and depressive disorders or suicide-related outcomes (Freire and Koifman, 2013). Nevertheless, their results were inconclusive in establishing a relationship between pesticide exposure and depression or suicide. However, later updated reviews seeking to attest a connection between occupational pesticide exposure and depression or suicide in agricultural workers are not available, as far as we know. Despite several studies showing the impacts of pesticides on human and environmental health, they are widely used around the globe, and hazardous pesticides are commonly used as a suicide method. Therefore, understanding the relationship between pesticides, mental health, and suicide could provide scientific evidence about the need for protective measures targeting agricultural population leading to a reduction of depression and suicide indices. It is also important to consider that the impacts of depression on human health can be long-lived, persistent or recurrent and can dramatically compromise the person's ability to live a pleasant and productive life at home and at work (WHO, 2017).

The WHO's Mental health action plan 2013–2030 and WHO's Mental Health Gap Action Program (mhGAP) include the management of depression and prevention of self-harm/suicide among the priority conditions covered by interventions for people with mental disorders (WHO, 2016;WHOWorld Health Organizationand Food and Agriculture Organization of the United Nations FAO, 2016, WHOWorld Health Organizationand Food and Agriculture Organization of the United Nations FAO, 2019). Moreover, according to WHO, self-poisoning with pesticides contributes to an important cause of the world's suicides. Although self-poisoning by pesticide ingestion has variable toxicity, depending on the dose and type of pesticide used, data demonstrate that the herbicide paraquat is the most hazardous one, killing about half of all people who ingest it, since there is no treatment available to reverse the effects of its acute toxicity (WHO and FAO 2019a, b).

Considering that the risk factors for depressive disorders and suicide are not completely understood, the present work is focusing to systematically review previous studies investigating if farmer's occupational exposure to pesticides is a risk factor for depressive disorders, anxiety, and suicide-related outcomes, including suicidal ideation, suicide attempts or suicide death/mortality.

Section snippets

Methodology

The present study was developed under PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) (Page et al., 2021) and Joanna Briggs Institute Critical Appraisals (JBI) guidelines (Munn et al., 2015; Aromataris and Munn, 2020). The methods of analysis and inclusion criteria were specified, the systematic review protocol was deposited and it is available in PROSPERO registration number CRD42022316285 (Zanchi, Marins, and Zamoner, 2022). We systematically reviewed cohort,

Study selection

A total of 298 individual study records published until November 2020 were identified in our searches in electronic databases. A flowchart showing a brief overview of the identification, screening and selection of the studies included in this systematic review is demonstrated in Fig. 1. Following the eligibility criteria described previously, 255 studies were excluded (n = 66 for duplicates, n = 175 excluded after reading the abstract, without occupational exposure or not targeting farmers).

Discussion

Mood or affective disorders are the most prevalent mental illnesses. The extensive use of pesticides leads to serious concerns about the impacts of these compounds to health and particularly to mental health (Conti et al., 2018).

The results presented herein suggest that previous pesticide poisoning might cause mental disorders, as well as dementia, Parkinson, and Alzheimer diseases. The severity of intoxication and farmers who experienced more than a single pesticide poisoning presented high

Funding

This work was supported by grants from Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina (FAPESC) chamada pública FAPESC/MS-DECIT/CNPq/SES-SC - apoio a programa de pesquisa para o Sistema Único de Saúde (SUS) – PPSUS [grant number FAPESC/PPSUS/TO#2017TR1365 and grant number FAPESC/PPSUS/TO#2021TR000533]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq-Brazil) [grant number 433245/2018–2/CNPq-Brazil and grant number 313311/2021–8/CNPq-Brazil]; and Brazilian

Credit author statement

Ariane Zamoner: conceptualization, supervision, project administration, funding acquisition, Resources, Formal analysis, Writing- Reviewing and Editing; Mariane Magalhães Zanchi: Methodology; Study search and selection; Data extraction; Formal analysis and Writing; Katiuska Marins: Methodology; Study search and selection; Data extraction and Writing. All authors read and approved the final manuscript.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper

Acknowledgements

We acknowledge FAPESC, DECIT/CNPq/SES-SC, PPSUS, CAPES-PrInt, CNPq-Brazil, CAPES and PGFAR for grants and research scholarships. Mariane Magalhães Zanchi and Katiuska Marins are registered on Pharmacy Graduate Course/UFSC-Brazil (PGFAR/UFSC).

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