Phthalates may play a role in ADHD symptoms.

Jan 12, 2009

Kim, BN, SC Cho, Y Kim, MS Shin, HJ Yoo, JW Kim, YH Yang, HW Kim, SY Bhang and YC Hong. 2009. Phthalates exposure and attention-deficit/hyperactivity disorder in school-age children. Biological Psychiatry doi:10.1016/j.biopsych.2009.07.034.


Synopsis by Paul Eubig, DVM

Phthalate chemicals create the softer, more flexible plastics used in many consumer products. Recent research suggests that children exposed to phthalates have a softer ability to perform well in school, as evidenced by increased inattentive and hyperactive behavior.

A new study finds that exposure to phthalate chemicals may be linked to attention-deficit/hyperactivity disorder (ADHD) in school-aged children. The Korean students in the study who were identified as having ADHD symptoms were more likely to have higher levels of phthalate chemical markers in their urine than children without symptoms of the disorder.


This is the first study in people to find a link between the two and supports previous results reported in rodent studies. The new research suggests chemical exposure may play a role in development of the disorder.

ADHD is a common behavioral disorder marked by impulsive behavior, overly active movement and lack of attention. It is currently estimated that approximately 6-7 percent of children in the United States have ADHD.

Although its causes are very complex, most doctors and scientists who study the disorder agree imbalances in the brain's chemical signals play an important role in its development. Experts question whether chemicals in the environment might influence the balance of the chemical signals and contribute to the development of ADHD symptoms.

To begin to answer that question, researchers in the study evaluated more than 250 Korean children for ADHD symptoms (through testing and teacher surveys), measured levels of phthalate markers in their urine and compared the two. Personal and social differences were statistically controlled.

They found that 8 to 11-year-old children who had higher levels of breakdown products of one type of phthalate (DEHP) in their urine were more likely to demonstrate inattentive and hyperactive behavior. Additionally, higher levels of the break-down product of a different type of phthalate (DBP) were associated with inattentive and impulsive performance on a standardized behavioral test.

Phthalates are a class of chemicals best known for their roles in keeping plastics soft and liquids mixed. Phthalates are very common in consumer products and may be found in perfumes and other personal care products; medications; food packaging; medical devices and vinyls.

People contact the chemicals through food, air, dust and skin. Recent studies show almost all Americans have detectable levels in their urine. Phthalates have been linked to several reproductive health changes although studies to date have mixed results. 

Because phthalates leave the body rather quickly, the study's results reflect recent exposure rather than past exposures. Yet, the roots of ADHD likely extend back to early development in the womb. To know the mothers' phthalate levels during pregnancy would aid in further understanding the relationship between long-term chemical exposure and the disorder.

In spite of this, the study suggests evidence for a role of early exposure to phthalates in the development of ADHD and indicates that the relationship should be more closely scrutinized.