Adolescents who are exposed to high levels of pesticides may be at greater risk for depression, according to a new study of Ecuadorian teens living in agricultural communities.
The findings, published in the journal International Journal of Hygiene and Environmental Health, suggest that the link is even stronger among girls and younger teens under 14 years.
Researchers from the University of California, San Diego, have been tracking the development of children living near agriculture in the Ecuadorian Andes since 2008. In this latest study, they observed 529 adolescents between the ages of 11 and 17.
Ecuador is the world’s third-largest exporter of roses, with much of the flower production located near the homes of the study 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.
Previous research has demonstrated that cholinesterase inhibition is associated with behaviors of anxiety and depression in mice, and a few existing studies in humans have also suggested such a link; however, prior pesticide exposure research in humans has only been established by self-reported exposure and not through biological measures.
The new findings confirm the researchers’ hypothesis: Adolescents who had lower AChE activity — suggesting greater exposure to cholinesterase inhibitors — exhibited more symptoms of depression, which was measured using a standardized depression assessment tool.
Notably, the link between low AChE activity and depression was stronger for girls (who made up half of all participants) and for teens younger than 14 years.
“Agricultural workers and people in these communities have long offered anecdotal reports of a rise in adolescent depression and suicidal tendencies,” said study leader Jose R. Suarez-Lopez, M.D., Ph.D., assistant professor in the Department of Family Medicine and Public Health at the University of California, San Diego School of Medicine.
“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.”
Symptoms of teen depression may include irritability, severe feelings of sadness, loss of interest or pleasure in usual activities and feelings of worthlessness or guilt.