Can Prenatal Acetaminophen Exposure Cause Autism and ADHD Symptoms?

Acetaminophen, a.k.a. paracetamol, is one of the most commonly-used over-the-counter remedies for pain and fever.   First discovered in 1877, it has long been considered safe if used at recommended levels and is included on the World Health Organization's Model List of Essential Medicines.   Long seen as harmless for pregnant women, acetaminophen has been used extensively to help alleviate pain and discomfort.   But a new study published in the International Journal of Epidemiology raises serious concerns about the prenatal risks associated with acetaminophen, including the development of autism-spectrum disorders and hyperactivity.   It is also one of the first studies showing different effects on boys and girls.  220px-Paracetamol-skeletal.svg[1]

A team of Spanish researchers led by Claudia Avella-Garcia of Barcelona's Center for Research in Environmental Epidemiology (CREAL) examined 2644 mother-child pairs recruited during pregnancy.   Follow-up assessments were conducted with 88 percent of the mother-child pairs when the children were one year old and 79.9 percent when they were five years old.  Along with structured interviews for the mothers, the children were tested with a series of psychometric measures including the Childhood Autism Spectrum Test (CAST), Conner’s Kiddie Continuous Performance Test (K-CPT), and ADHD-DSM-IV form list.  

In the structured interviews, mothers were questioned about their acetaminophen use during pregnancy.   Since mothers could not recall exact doses taken, they were rated as either ever/never used acetaminophen and for those who reported use, being rated as sporadic or persistent use. 

Results showed 43 percent of children at age one and 41 percent of children at age five had at least some exposure to acetaminophen while their mothers were pregnant.  When assessed at age five, exposed children were found to be higher risks for developing hyperactivity or impulsivity symptoms.    On tests measuring visual speed processing and inattention, exposed children score much more poorly than unexposed children.   There are also significant gender differences with boys being more likely than girls to develop autism spectrum symptoms following prenatal exposure to acetaminophen.    While the researchers focused on autism spectrum symptoms instead of whether children were formally diagnosed with autism, the range of symptoms linked to prenatal acetaminophen and the impact on the later development is disturbing.

When asked when acetaminophen could have an impact on brain development in children, co-author Dr. Jordi Júlvez, suggested in an interview: “Paracetamol could be harmful to neurodevelopment for several reasons. First of all, it relieves pain by acting on cannabinoid receptors in the brain.  Since these receptors normally help determine how neurons mature and connect with one another, paracetamol could alter these important processes.  It can also affect the development of the immune system, or be directly toxic to some fetuses that may not have the same capacity as an adult to metabolize this drug, or by creating oxidative stress.”  Male brains my be more vulnerable to the effects of acetaminophen due to disruptions in male hormone production for which female brains would be much less likely to be affected.

Though the researchers stress that more studies are needed, they suggest that widespread exposure to acetaminophen, which continues to be used extensively during pregnancy, can lead to a surge in ADHD and autism-spectrum cases.   Medical doctors and patients need to be more aware of potential risks and weight them against the benefits involved.

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