Roses are pretty but as a result of modern farming methods there is more to fear than thorns. It turns out an elevated risk for depression in teens has been established as a result of the pesticides sprayed on the flower fields of Ecuador.

Researchers from the University of California San Diego School of Medicine have been tracking the development of children living near the agricultural areas in the Andes region of Ecuador since 2008. They have been trying to understand what effect, if any, pesticide use has on the workers and residents living near the farms.

Dr. Jose Suarez-Lopez studied 529 adolescents between the ages of 11 and 17 and published his findings in the International Journal of Hygiene and Environmental Health. He was able to establish a direct link between pesticide use and depression in the teens.

"Agricultural workers and people in these communities have long offered anecdotal reports of a rise in adolescent depression and suicidal tendencies," said Suarez-Lopez. "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."

Ecuador is the third-largest exporter of roses in the world and many of the workers live in close proximity to the fields. That not only exposes the growers but their families to the organophosphate insecticides used on the flower fields, the same pesticides sprayed on many other agricultural crops in Ecuador and around the world.

Researchers say these chemicals are known to affect the human cholinergic system, which is a key system in the function of the brain and nervous system.

Dr. Suarez-Lopez and his team measured the levels of the enzyme acetylcholinesterase (AChE) in the children. Organophosphate pesticides have been shown to inhibit AChE activity, which in other studies caused anxiety and depression in mice and self-reported anxiety symptoms in humans. This is the first study to show a direct link using biological measures.

The greater the exposure to cholinesterase inhibitors the greater the depression symptoms as measured by a standardized depression assessment tool. The effects were greater in girls and children under the age of 14.

This information comes on the heels of another study by the same UCSD researchers who found children ages 4-9 experiencing elevated blood pressure as a result of pesticide exposure.

Click here to read more in the International Journal of Hygiene and Environmental Health.