07
Jun
Pesticides and Neurotoxicity: The Link Between Mood Disorders and Pesticides Exposures
(Beyond Pesticides, June 7, 2023) A systematic review of scientific literature published in Environmental Research on the development of mood disorders among pesticide applicators (farmers, landscapers, etc.) finds an increased risk of depression symptoms over the last decade. The evidence in the review highlights the presence of pesticide-specific biomarkers and biomarkers of depression that determine the positive association between pesticide exposure and the development of depressive symptoms. With more high-quality longitudinal studies to control sociocultural variables, researchers can directly pinpoint risks of developing depression, especially among agricultural workers and landscapers who use pesticides.
Research on pesticide-induced diseases commonly investigates pesticide exposure concerning the development of various physical illnesses. However, previous studies show that occupational (work-related) risks of developing depression are high in agriculture, where pesticide use is rampant. Acute exposure to chemicals, including organophosphate, organochlorine, triazine, and carbamate pesticides, tends to put farmers at greater risk of suicide than the general population. There is a lack of information connecting pesticide exposure to the subsequent psychological (psychiatric) effects on the general population. Additionally, household pesticide exposure varies from occupational exposure via exposure frequency, duration, intensity, and type.
According to the World Health Organization (WHO), depression affects 322 million people globally, with the number of diagnosed patients increasing by 18.4% from 2005 to 2015. Although the etiology of depression—and many other psychiatric disorders—is often genetic, studies suggest that other etiological factors, like pesticide exposure, play a role in depression incidents. Poor mental health has a tangible influence on physical health (e.g., depression and cardiovascular disease); therefore, the combination of pesticide exposure and mental illness worsens the adverse effects on human health. If pesticide exposure exacerbates psychiatric disorder symptoms, it is important to evaluate how pesticide exposure affects mental health, in addition to physical health. This research highlights the significance of researching potential mental health detriments resulting from pesticide exposure, especially as society tends to rank mental health risks second to physical health. The study notes, “Given the rise in pesticide use in agriculture, the low adherence of farmers to safety training, and the health risks associated with depression, it is recommended to implement stricter surveillance measures on agricultural companies and monitor the mental health of exposed workers. It is also important to actively involve the community in prevention and intervention efforts.”
The review conducted a thorough scientific literature search on occupational pesticide exposure and depression symptom development in the PubMed and Scopus databases from the last ten years (2011 to September 2022). Using guidelines recommended by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and the Population, Exposure, Comparison, and Outcomes (PECO) strategy, researchers examined the association between occupational exposure to pesticides and symptoms of depression in agricultural workers. Among the reviewed articles, 78 percent indicate a link between exposure to pesticides and the prevalence of depression symptoms. Most pesticides associated with depressive symptoms include organophosphate insecticides, general herbicides, and pyrethroid insecticides.
For over two decades, research concerning pesticide exposure and psychiatric disorders, such as depression, focused on occupational hazards, especially for agricultural farmworkers. Exposure to agricultural pesticides puts farmers at a six times greater risk of exhibiting depressive symptoms, including chronic anxiety, irritability, restlessness, and sadness. Specifically, exposure to organochlorines and fumigants (gaseous pesticides) heighten an individual’s risk of depression by 90% and 80%, respectively. Organochlorines are chemicals of concern as they can induce a myriad of health problems, including reproductive dysfunction, endocrine disruption, cancer, and fetal defects. Though the U.S. bans the use of many organochlorines, these chemicals can still expose individuals to volatile concentrations as they are highly persistent in the environment. Fumigants are a human health concern as many fumigants are gases that can cause acute toxicity upon inhalation and ingestion. Linear models reveal an association between lifelong pesticide poisoning episodes and the increased risk of developing mental disorders among tobacco farmers. Tobacco farmers using organophosphate pesticides have a higher prevalence of minor psychiatric disorders. Organophosphates are a family of insecticides derived from World War II nerve agents. They are cholinesterase inhibitors, meaning they bind irreversibly to the active site of an essential enzyme for normal nerve impulse transmission, acetylcholine esterase (AchE), inactivating the enzyme.
Individuals suffering from occupational pesticide exposure face a disproportionate risk of developing depression. However, pesticide exposure from nearby agricultural fields remains a threat to residential (nonoccupational) human health. Previous studies found that populations living near farms are more likely to have high depressive symptoms. Similarly, a 2019 study found that teens and adolescents living in agricultural areas, where organophosphate exposure is prevalent, are at higher risk of depression. Uniquely, gender (female), physical health, and age (young adult) indicate likely of having depressive symptoms, with the most adverse effects on women, those in poor physical health, and children under 14.
Understanding the mental health implications of conventional pesticide exposure can help identify the various physiological mechanisms attributed to psychiatric disorders. Like this review, past research finds that organophosphates have significant associations with depressive symptom development, including disturbing normal nerve impulses. So, scientists can analyze information to determine if the lack of normal nerve impulses contributes to non-pesticide-induced depression.
Whether pesticide exposure is occupational or residential, the development of depression symptoms is of concern. Annually, only half of Americans with a depression diagnosis seek treatment for symptoms. Untreated symptoms of depression can increase the risk of suicide, a severe sign of depression. Commonalities between occupational and household pesticide exposure are suicidal thoughts and pesticide provocation as a suicide agent. A study published in the WHO Bulletin found that people storing organophosphate pesticides in their homes are more likely to have suicidal thoughts as the exposure rate is higher. The study found an association between suicidal thoughts and ease of household pesticide accessibility. Geographic areas with more frequent home storage of pesticides have higher rates of suicidal thoughts than the general population. WHO scientists recognize pesticide self-poisoning as one of the most significant global methods of suicide, as increases in pesticide toxicity make them potentially lethal substances. Robert Stewart, Ph.D., a researcher for the WHO Bulletin, stated that: “Organophosphate pesticides are widely used around the world. They are particularly lethal chemicals when taken in overdose and are a cause of many suicides worldwide.” With that in mind, researchers say it is vital to recognize how pesticide exposure and accessibility can influence mental illnesses.
To address health issues regarding pesticide exposure and mental health incidents, health care providers must have sufficient information on signs and symptoms of chemical exposure. Farmers, landscapers, and other individuals encountering chemical exposure through ingestion, inhalation, and skin (dermal) contact are unaware of the non-physical side effects. Considering depression related to acute pesticide exposure may persist long after initial exposure, those working with toxic pesticides must have adequate protective equipment to minimize exposure. Therefore, government agencies should assess the provocation of psychiatric disorders accompanying acute and chronic pesticide exposure to protect human health. Given the rise in mental health problems among agricultural workers and the potential health risks, including depression and other severe conditions that can affect their well-being, analyzing existing studies is crucial. Accordingly, this review aims to organize the scientific evidence from the last decade regarding the impact of occupational exposure to pesticides on the development of depression symptoms among agricultural workers.
The study concludes “[…] that governments worldwide bear greater responsibility in addressing this matter, which could help control the various systemic sources of exposure to pesticides and other environmental pollutants and lessen the harm to the health of workers.”
Mental health is just as—if not more–important than physical health, and reviews such as this highlight the importance of knowing pesticide implications beyond physical ailments. Through our Pesticide Induced Diseases Database (PIDD), Beyond Pesticides tracks the most recent studies related to pesticide exposure. For more information on the multiple harms of pesticides, see PIDD pages on brain and nervous system disorders, endocrine disruption, cancer, and other diseases. Additionally, buying, growing, and supporting organic can help eliminate the extensive use of pesticides in the environment. Our choices encourage the protection of the people who help put food on our table every day by purchasing organic products. By buying and using organic products, you not only support an agricultural system that does not heavily rely on the widespread application of dangerous pesticides but also put a residential system. For more information on how organic is the right choice for consumers and the farmworkers that grow our food, see the Beyond Pesticides’ webpage, Health Benefits of Organic Agriculture.
Lastly, suicide is the tenth leading cause of death among adults (3rd for adolescents) in the U.S., with more than 34,000 individuals succumbing to the disease annually. Suicidal thoughts and behaviors are dangerous and harmful and are therefore considered a psychiatric emergency. An individual experiencing these thoughts should seek immediate assistance from a health or mental health care provider. If you or someone you know is in an emergency, call the National Suicide Prevention Lifeline at 1-800-273-TALK (8255) or 911 immediately.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Research
