High Rates of Suicide, Depression Linked to Farmer Use of Pesticides

http://www.scientificamerican.com/article/high-rates-of-suicide-depression-linked-to-farmer-use-of-pesticides/?WT.mc_id=SA_HLTH_20141007

Oct 6, 2014 |By Brian Bienkowski

•••••

Farming is a stressful job – uncontrollable weather, physical demands and economic woes intertwine with a personal responsibility for land that often is passed down through generations. But experts say that some of the chemicals used to control pests may make matters worse by changing farmers’ brain chemistry.

Recent research has linked long-term use of pesticides to higher rates of depression and suicide. Evidence also suggests that pesticide poisoning – a heavy dose in a short amount of time – doubles the risk of depression.

“For years there was a high level of denial in the farming community that mental illness exists, period,” said Lorann Stallones, an epidemiologist and psychology professor at Colorado State University. “But there’s been a shift – partly because there’s more people talking about being mentally incapacitated.”

•••••

Peters and his wife were among 89,000 farmers and other pesticide applicators in Iowa and North Carolina who have participated in the Agricultural Health Study led by the National Institute of Environmental Health Sciences.

Last month, epidemiologist Freya Kamel and her colleagues reported that among 19,000 studied, those who used two classes of pesticides and seven individual pesticides were more likely to have been diagnosed with depression. Those who used organochlorine insecticides were up to 90 percent more likely to have been diagnosed with depression than those who hadn’t used them. For fumigants, the increased risk was up to 80 percent.

•••••

The studies don’t prove that pesticides cause depression, but animal testing indicates that it’s possible, said Cheryl Beseler, an environmental health researcher at Colorado State University. In rat tests pesticides have altered brain cells, neurotransmitters and production of a protective acid.

In France, farmers who used herbicides were nearly twice as likely to have been treated for depression than those who didn’t use herbicides, according to a study published last year. The study of 567 farmers found that the risk was even greater when the herbicide applicators had been doing it for more than 19 years.

The studies suggest that chronic exposure to low levels over time may raise the risk of depression.

•••••

Most insecticides work by disrupting insects' nerve cells. At high enough doses, they can alter human nerve cells as well.

“I don’t think there’s any question that pesticides can affect the functions of the brain,” Kamel said, referring to experiments that found pesticides harm rats' brain tissue and receptors. “There could also be indirect effects. Pesticides can promote other health problems, which could be related to depression.”

For instance, Dr. Beate Ritz, a neurologist and professor at the University of California, Los Angeles, found that Californians exposed to pesticides are more likely to have Parkinson’s disease. One effect of the neurological disease, characterized by a lack of the chemical dopamine, is depression.

•••••

Several studies have linked suicide to pesticide use. In Brazil, workers that used more pesticides were more likely to commit suicide, and in China, a World Health Organization survey of 9,800 people in the rural Zhejiang province revealed that those who stored pesticides in their homes had more than double the risk of having suicidal thoughts.

•••••