Pesticides and depression

The EPA is becoming increasingly interested in the long-term effects of neurotoxic pesticides on farmers. The famous case of DDT, a pesticide used to combat insects and malaria, was brought to the public after a study in the 1970s showed it endangering bald eagles’ eggs by thinning their egg shells. Researchers recently began to hypothesize that since insects’ nervous systems are being destroyed by fumigants and other chemicals, the long-term effects could affect the neurochemistry of farmers negatively. Farmers have the most exposure to the chemicals, and EPA regulations aren’t nearly as safe as they should be.
In a 2010 study, Italian researchers Angelo Moretto, Manuela Tiramani and Claudia Colosio recognized the difficulty in assessing psychological effects in the brain from long-term pesticide exposure. Behavior is wildly complex and results can only be expressed as a wide variety of functions from very detailed procedures. The study also states that “because of this complexity, a harmonized assessment is still lacking also because different approaches have been chosen by different researchers.” Data frequently ended up inconclusive on specific behavioral effects.

Epidemiologist Freya Kamel and her colleagues published a cohort study last month on the long-term behavioral effects on 19,000 farmers. Kamel and her colleagues collected data by imitating an earlier cohort study to get comparable results. Farmers were more willing to share information about their mental condition compared to 20 years ago. They interviewed subjects when they enrolled and were interviewed once more at the completion of the study about 12 years later. Most cohort studies on pesticides only monitored depression.

The study reported these results: “In each case group, depression was positively associated with over-use of fumigants as a class and organochlorine insecticides as a class as well as the specific fumigants aluminum phosphide and ethylene dibromide; the phenoxy herbicide, acetic acid, the organochlorine insecticide dieldrin; and the OPs diazinon, malathion and parathion.” Farmers with the highest exposure to pesticides were 50 percent more likely to have a depression diagnostic in comparison to the same group in the ‘90s. A study published in the Journal of Environmental Biology recognized that organophosphate based pesticides affect rat nervous systems so human brain damage is possible.

However, the data collected was adjusted by the questionnaire the farmers took which included factors like age, location, education, family status, drug consumption, diabetes, farm size and safety. I feel that only considering these factors makes it difficult to directly associate depression caused by pesticide exposure. Wendy Ringgenberg, an assistant professor at the University of Iowa, searched through nearly two decades of national data on behavioral statistics. She mentioned that farmers feel occupational stress more than most people for many reasons, including long work hours, self-reliance, weather and changing politics. Furthermore, the increase in reported depression might be affected by the increasingly popular reports of other mental diseases in the farming community, such as Parkinson’s disease.
The EPA has canceled registrations of all the reported chemicals besides aluminum phosphide, diazinon and malathion, which are under review. Along with the majority of farmers in the United States, I am resistant to identifying depression as a mental illness, but I also recognize the potential of pesticides being able to cause extensive neurological damage.