One reason why GMO crops are favored by many farmers is that they reduce or eliminate the need for pesticide application. Splicing some of the genes of a common soil bacterium into the dna of corn and soybeans, for example, imbues the plants with an ability to fend off munching pests, obviating the need for pesticides.
Now data gathered and analyzed by researchers at National Institutes of Health indicate that farmers chronically exposed to pesticides and herbicides are at a significantly higher risk of developing suicidal depression.
To produce their report, released last month, a group of eight NIH epidemiologists surveyed 21,208 pesticide applicators in Iowa and North Carolina, asking them to report whether they had received a doctor’s diagnosis of depression between 1993 and 2010. In total, 1,701—eight percent—said they had. The researchers, who also examined the specific chemicals used by farmers to kill insects, weeds, and fungi, found that farmers who used one class of common insecticide were up to 90 percent more likely to have been diagnosed depression, and that farmers who used common fumigants were up to 80 percent more likely to be depressed.
Studies in rats indicate that chronic exposure alters brain cells and neurological chemistry:
“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.”
It's unsurprising, then, that epidemiological studies show higher per capita rates of depression and suicide in states with the most agriculture, such as California's central valley and the southern plantations in places like Mississippi and Alabama.