Common plasticizer may trigger lifelong anxiety-related behavioral changes

Male rats that were exposed to the widely used plasticizer di-(2-ethylhexyl) phthalate (DEHP) during early development exhibited increased anxiety behavior as adults, according to a study being presented Saturday at ENDO 2026, the Endocrine Society's annual meeting in Chicago, Ill.

While the research was performed in rodents, the work suggests humans exposed to endocrine disruptors before and shortly after birth may experience behavioral changes that last a lifetime.

This research demonstrates that one of the most widely used plasticizers worldwide is capable of causing behavioral changes when the subject is exposed during the prenatal and immediate postnatal developmental stages, with this effect lasting over time."

Osvaldo Juan Ponzo, M.D., Ph.D., professor of physiology, University of Buenos Aires School of Medicine, Buenos Aires, Argentina

DEHP is used in many plastic items to make them more flexible, such as medical devices, toys, shower curtains and raincoats. Numerous studies have shown that DEHP and its metabolites interfere with a number of organ systems in animals and humans, namely the reproductive and nervous systems. Scientists at the University of Buenos Aires School of Medicine wanted to examine the effects of DEHP on anxiety-like behavior in adult male rats and determine whether the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) or testosterone was involved in regulating this action.

Pregnant female rats were given DEHP orally every day, starting with the first day of gestation until they weaned their litter. After male pups reached maturity at 70 days old, the research team evaluated their anxiety-like behaviors by placing them in an elevated plus maze (EPM), a test based on the natural aversion of rodents to open spaces and heights. The EPM is shaped like a plus symbol and has two open and two closed arms. The scientists could gauge how often and how long the rats stayed in both arms, as well as how long they remained motionless, known as freezing time.

Ninety minutes before EPM testing, some of the animals were treated with GABA agonists-molecules that bind and activate GABA-while other animals received testosterone every 48 hours for 14 days prior to the test. The scientists observed that the DEHP-only group demonstrated anxiety-like behavior, spending less time exploring open arms and more time in the closed arms of the maze. They also had increased freezing time. However, the DEHP rats treated with GABA agonists and testosterone displayed the opposite characteristics.

"This work demonstrates that contact with DEHP in the early stages of life could modify behavior with regard to anxiety, even in the absence of DEHP exposure in adulthood," Ponzo said. "These neuroendocrine changes can be reversed by treating with GABA agonists or testosterone."