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

Depressive symptoms and suicide attempts among farmers exposed to pesticides

Pesticides safeguard crop health but may diminish cholinesterase activity in farmers, potentially leading to psychiatric disorders like depression and suicide attempts. This study, with 453 participants (225 pesticide-exposed farmers, 228 non-farmers) in Almería, Spain, aimed to investigate the presence of depressive symptoms and suicide attempts, the decrease acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activity, and their relationship with pesticide exposure in farmers. Depressive symptoms were evaluated using the Spanish adaptation of the Beck Depression Inventory, and blood samples were analyzed for AChE and BChE activity. Farmers showed significantly increased risk of moderate/severe depression and suicide attempts compared to non-farmers (OR = 2.18; p = 0.001), with highest risks observed among mancozeb users (OR = 2.76; p = 0.001 for depression) and malathion users (OR = 3.50; p = 0.001 for suicide attempts). Findings emphasize elevated depression and suicide risks among pesticide-exposed farmers, particularly associated with chlorpyrifos, mancozeb, and malathion exposure.

Neurogenesis and pesticides: news of no new neurons

New hippocampal neurons are continuously generated in the adult human brain. Several studies have demonstrated that the proliferation of hippocampal cells is strongly influenced by a variety of stimuli, including pesticides exposure. These effects are particularly important because neurogenesis dysregulation could be associated with the decline of neuronal and cognitive functions and the possible development of neuropsychiatric disorders.

Association of pesticide exposure with neurobehavioral outcomes among avocado farmworkers in Mexico

BACKGROUND AND AIM

To date, few studies have focused on the health effects of pesticide exposure among avocado farmworkers. We examined the association of exposure to insecticides, fungicides, and herbicides with cognitive and mental health outcomes among these avocado workers from Michoacan, Mexico.

MATERIALS AND METHODS

We conducted a cross-sectional study of 105 avocado farmworkers between May and August 2021. We collected data on self-reported pesticide use during the 12 months prior to the baseline survey and estimated annual exposure-intensity scores (EIS) using a semi-quantitative exposure algorithm. We calculated specific gravity adjusted average concentrations of 12 insecticide, fungicide, or herbicide metabolites measured in urine samples collected during two study visits (8-10 weeks apart). We assessed participants' cognitive function and psychological distress using the NIH Toolbox Cognition Battery and the Brief Symptom Inventory 18 (BSI-18), respectively. We examined individual associations of EIS and urinary pesticide metabolites with neurobehavioral outcomes using generalized linear regression models. We also implemented Bayesian Weighted Quantile Sum (BWQS) regression to evaluate the association between a pesticide metabolite mixture and neurobehavioral outcomes.

RESULTS

In individual models, after adjusting for multiple comparisons, higher concentrations of hydroxy-tebuconazole (OH-TEB, metabolite of fungicide tebuconazole) were associated with higher anxiety (IRR per two-fold increase in concentrations = 1.26, 95% CI:1.08, 1.48) and Global Severity Index (GSI) (IRR = 1.89, 95% CI:1.36, 2.75) scores, whereas higher concentrations of 3,5,6-trichloro-2-pyridinol (TCPy, metabolite of chlorpyrifos) were associated with lower GSI scores (IRR = 0.69, 95% CI: 0.56, 0.85). In BWQS analyses, we found evidence of a mixture association of urinary pesticide metabolites with higher anxiety (IRR = 1.72, 95% CrI: 1.12, 2.55), depression (IRR = 4.60, 95% CrI: 2.19, 9.43), and GSI (IRR = 1.99, 95% CrI: 1.39, 2.79) scores. OH-TEB and hydroxy-thiabendazole (metabolite of fungicide thiabendazole) combined contributed 54%, 40%, and 54% to the mixture effect in the anxiety symptoms, depression symptoms, and overall psychological distress models, respectively.

CONCLUSIONS

We found that exposure to tebuconazole and thiabendazole, fungicides whose effects have been rarely studied in humans, may be associated with increased psychological distress among avocado farmworkers. We also observed that exposure to chlorpyrifos may be associated with decreased psychological distress.

What Do Farmers Need for Suicide Prevention: Considerations for a Hard-to-Reach Population

Purpose

Farmers have suicide rates much higher than the general population, with elevated mental health symptoms and high stress levels. Farmers are a hard-to-reach population due to occupational demands and a culture where conversations about mental health are often stigmatizing. This study explored ways to tailor suicide prevention strategies to unique characteristics of farmers by speaking with groups close to farmers who were open to discussing stress and suicide prevention: women married to farmers and agricultural Extension agents.

Methods

Focus groups with women married to farmers (N=29) and interviews with agricultural agents from the university's local Cooperative Extension offices (N=13) from rural Georgia counties explored effective ways outreach and education about suicide prevention, mental health, and coping could be provided to farmers. Using a thematic analysis approach, qualitative coding was completed by two researchers (Cohens kappa=0.86), with initial codes collapsed into common themes.

Results

Four themes were identified: 1) Barriers due to the nature of farming, including time demands of farming and cultural stigma in help-seeking; 2) Acceptable messaging, including framing conversations as part of general health; 3) Make information accessible by making it brief, clear, and omnipresent through multiple media; and 4) Elements of effective information and education, including emphasizing "you're not alone" and connection, how to access supports and crisis services, educating people close to farmers, and motivating farmers by emphasizing that they could help another farmer with the information.

Conclusion

Due to farmers' stoic identities and reluctance to admit mental health struggles, speaking with those close to farmers may help us better understand what is needed to tailor farmer suicide prevention strategies. The insights shared by participants suggest that culturally responsive outreach and education strategies, strengthening relationships through peer support, and gatekeeper training with specific trusted others are important ways to tailor suicide prevention strategies for this hard-to-reach group.

Pesticide Exposure or Pesticide Poisoning and the Risk of Depression in Agricultural Populations: A Systematic Review and Meta-Analysis

Evidence suggests that farm workers represent a high-risk population for the development of depression. The aim of the study was to clarify the association between pesticide exposure/poisoning and depression. The Preferred Reporting Items for Systematic Reviews and Meta-Analysis were conducted in this systematic review and meta-analysis. Relevant studies were included through searching in PubMed, Scopus, Web of Science, ProQuest, CINAHL and pre-print services databases. A total of eight studies were included. A positive but non-significant association was observed between pesticide use and depression (OR = 1.123; 95% CI, 0.932-1.354, p-value = .221) while a significant positive association was observed between pesticide poisoning and depression (OR = 2.942; 95% CI, 1.791-4.831, p-value < .001). The present meta-analysis suggested clearly a significant positive association between pesticide poisoning and depression, confirming the hypothesis that pesticide poisoning is a risk factor of depression. It also revealed positive, yet non-significant association, between pesticide exposure and depression, a finding that enhances recent research but requires to be further supported by future cohort studies, including socioeconomic factors and biomarkers of depression.

Organophosphate ester flame retardants and plasticizers in house dust and mental health outcomes among Canadian mothers: A nested prospective cohort study in CHILD

Organophosphate ester flame retardants and plasticizers (OPEs) are common exposures in modern built environments. Toxicological models report that some OPEs reduce dopamine and serotonin in the brain. Deficiencies in these neurotransmitters are associated with anxiety and depression. We hypothesized that exposure to higher concentrations of OPEs in house dust would be associated with a greater risk of depression and stress in mothers across the prenatal and postpartum periods. We conducted a nested prospective cohort study using data collected on mothers (n = 718) in the CHILD Cohort Study, a longitudinal multi-city Canadian birth cohort (2008-2012). OPEs were measured in house dust sampled at 3-4 months postpartum. Maternal depression and stress were measured at 18 and 36 weeks gestation and 6 months and 1 year postpartum using the Centre for Epidemiologic Studies for Depression Scale (CES-D) and Perceived Stress Scale (PSS). We used linear mixed models to examine the association between a summed Z-Score OPE index and continuous depression and stress scores. In adjusted models, one standard deviation increase in the OPE Z-score index was associated with a 0.07-point (95% CI: 0.01, 0.13) increase in PSS score. OPEs were not associated with log-transformed CES-D (β: 0.63%, 95% CI: -0.18%, 1.46%). The effect of OPEs on PSS score was strongest at 36 weeks gestation and weakest at 1 year postpartum. We observed small increases in maternal perceived stress levels, but not depression, with increasing OPEs measured in house dust during the prenatal and early postpartum period in this cohort of Canadian women. Given the prevalence of prenatal and postpartum anxiety and the ubiquity of OPE exposures, additional research is warranted to understand if these chemicals affect maternal mental health.

Glyphosate-induced glioblastoma cell proliferation: Unraveling the interplay of oxidative, inflammatory, proliferative, and survival signaling pathways

The aim of the present study was to investigate the impacts of glyphosate herbicide on the survival and proliferation of glioblastoma cells and to explore the molecular mechanisms underlying such effects. For this, cultured human glioblastoma cell line, A172, was exposed to the glyphosate analytical standard, a glyphosate-based herbicide formulation (GBH), or the metabolite aminomethylphosphonic acid (AMPA). The three compounds induced A172 cytotoxicity after 24 h of exposure, with more prominent cytotoxic effects after 48 and 72 h of treatment. Further experiments were performed by treating A172 cells for 6 h with glyphosate, GBH, or AMPA at 0.5 mg/L, which corresponds to the maximum residue limits for glyphosate and AMPA in drinking water in Brazil. Colony forming units (CFU) assay showed that AMPA increased the number of CFU formed, while glyphosate and GBH increased the CFU sizes. The three compounds tested altered the cell cycle and caused DNA damage, as indicated by the increase in γ-H2AX. The mechanisms underlying the pesticide effects involve the activation of Akt and mitogen-activated protein kinases (MAPKs) signaling pathways, oxidative imbalance, and inflammation. Glyphosate led to NLRP3 activation culminating in caspase-1 recruitment, while AMPA decreased NLRP3 immunocontent and GBH did not alter this pathway. Results of the present study suggest that exposure to glyphosate (isolated or in formulation) or to its metabolite AMPA may affect cell signaling pathways resulting in oxidative damage and inflammation, giving glioblastoma cells an advantage by increasing their proliferation and growth.

Agricultural activities and risk of treatment for depressive disorders among the entire French agricultural workforce: the TRACTOR project, a nationwide retrospective cohort study

Background

Although depression is a major issue among farming population, to date, there have been few studies on specific agricultural activities. We aimed to investigate whether, among the entire French farm manager (FM) workforce, certain agricultural activities are more strongly associated with depression than others.

Methods

This nationwide retrospective cohort study used data from an administrative health database available to the TRACTOR project. This database pertains to the entire French agricultural workforce (overseas workers not included). Data were analyzed from January 2021 to December 2022. All FMs that worked at least once over the period 2002-2016 were included. The outcome measure was the association between 26 agricultural activities and the risk of depression measured as hazard ratios (HRs) after adjusting for age, sex, and pre-existing medical comorbidities. The time to first depression insurance declaration, or first antidepressant prescription claim was used as the underlying timescale. For each activity, the reference/control group included all FMs that never performed the considered activity between 2002 and 2016, while the exposed group included FMs that performed the considered activity at least once from 2002 to 2016. Four sensitivity analyses were conducted to test hypotheses, and to address potential sources of bias.

Findings

There were 84,507 (7.76%; 28.2 cases per 1000 person-years) depression cases among 1,088,561 FMs (mean age 46.6 [SD 14.1]). Compared to other activities, dairy farming (HR = 1.37, 95% confidence interval: 1.32-1.42), cow farming (HR = 1.53 [1.47-1.59]), poultry and rabbit farming (HR = 1.37 [1.27-1.50]), and mixed farming (HR = 1.30 [1.24-1.36]) were more strongly associated with depression. Sex differences were observed, with most of the time, risks higher for females than for males.

Interpretation

Agricultural activities at risk of depression among the entire French agricultural workforce were identified. These findings do represent a crucial first step on the road to implement effective preventive measures against depression to determine where additional resources should be allocated to screen for depression, along with intervention.

Funding

MIAI@Grenoble Alpes, and Mutualité Sociale Agricole.