Pesticide exposure linked to depression in teens, study says

Adolescents exposed to elevated levels of pesticides are at an increased risk of depression, according to a new study published in the International Journal of Hygiene and Environmental Health.

Led by Jose Suarez-Lopez, MD, PhD, assistant professor at the University of California San Diego School of Medicine, researchers examined 529 adolescents between the ages of 11 and 17 years old in Ecuador, the world's third-largest exporter of roses, with much of the flower production located near the homes of participants. 

Like many other agricultural crops, flowers are routinely sprayed with organophosphate insecticides, which are known to affect the human cholinergic system, a key system in the function of the brain and nervous system.

To test exposure levels of children, the research team measured levels of the enzyme acetylcholinesterase (AChE) in the blood. Pesticides such as organophosphates and carbamates exert their toxicity by inhibiting AChE activity. Past studies have shown that cholinesterase inhibition is linked to behaviors of anxiety and depression in mice, and a few existing studies in humans have also suggested such a link; however, pesticide exposure assessment in past studies had been only established by self-report of exposure and not using biological measures.

The results confirmed teens who had lower AChE activity, suggesting greater exposure to cholinesterase inhibitors, showed more symptoms of depression assessed using a standardized depression assessment tool. Notably, the association was stronger for girls, who comprised half of all participants, and for teens younger than 14 years, according to the study abstract.

"Agricultural workers and people in these communities have long offered anecdotal reports of a rise in adolescent depression and suicidal tendencies," said Suarez-Lopez in a statement. "This is the first study to provide empirical data establishing that link using a biological marker of exposure, and it points to a need for further study."