Tylenol and Autism: What are the Facts?
In September, the US Department of Health and Human Services, the government agency tasked with safeguarding public health research and health-related social services for Americans, advised caution regarding the use of Acetaminophen (brand name Tylenol) during pregnancy. The claim is that studies have shown a connection between Tylenol use during pregnancy and the incidence of neurodivergence in the products of those gestations. Much of this contention rests on the results of an observational 2017 study out of Norway that alleged a clinically-significant correlation between Tylenol use during pregnancy and ADHD or Autism in the resultant offspring.
Several more recent larger-scale studies failed to confirm this conclusion. Specifically, research that investigates health conditions in siblings indicates that a complex combination of biologic and environmental factors contribute to the development of neurodivergent traits. An NIH-funded study out of Sweden included nearly 2.5 million children over a span of six years, and demonstrated that when sibling data is taken into account, there was no increase in neurodivergence in products of pregnancies in which Tylenol was used. Siblings share genetics and are raised in similar circumstances, so including them in the population of any given study tends to negate outlying factors.
To date, there is no conclusive evidence that Tylenol taken during pregnancy contributes to the development of Autism. An overly-simplified approach to data can erroneously suggest a link, much like someone could claim “100% of people who drink water die eventually, therefore drinking water causes death.” Indeed, pregnant mothers with severe pain or fever during their gestation— conditions that might prompt them to ingest Tylenol— may have higher incidences of neurodivergent offspring due to the insult that compelled seeking pain- and fever-relief of Acetaminophen. It’s myopic to ignore that other variables likely play a role in the multifactorial development of neurodevelopmental disorders. It is also nearly impossible to gather accurate information about Tylenol ingestion from chart reviews, since it’s available over the counter and unless its use is subjectively reported, it will not show up on a digital medical record’s prescription medication list.
In an exhaustive review of the literature that was published this year in the International Journal of Molecular Sciences, a team of researchers takes a deep dive into the side effects of pregnancy (including theories that posit reduced levels of glutathione) and the metabolism of Tylenol (including claims of mitochondrial oxidative stress) and, in the end, concluded only that these circumstances could occur, not that they necessarily do, were proven to exist, or can be causally linked to ADHD, Autism, or any specific pregnancy outcome.
Neurodivergence is an imperfect area of medical study. To date, there is no MRI or blood test that can definitively diagnose a patient with ADHD or Autism. These labels are based on subjective assessments of a constellation of observed and reported symptoms. Their development is part of a complex combination of genetics, gestational risk factors, and environmental inputs. To distill this years-long progression to an oversimplified cause-and-effect is an insult to the intelligence of the audience and raises undue alarm for expectant parents who are already in a high-stress emotional state.
