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Why We STILL Give Acetaminophen to Babies

By: Dr. William Parker

With overwhelming evidence that acetaminophen causes autism, why are we still giving acetaminophen to our babies and children? This is one of the most common questions I get as a followup to explaining the evidence. The answer is very complex.

Some of the answers are as follows:


  1. The FDA does not have a standard mechanism to pull back a drug that has been in use for decades. This requires special action. Such action has happened before with aspirin, when it was connected with Reye Syndrome. That effort took grassroots movement and a lawsuit here in the US. So far, there is not yet sufficient support for change to be implemented in this way.

  2. Many physicians and pharmacists are incredulous, despite overwhelming evidence. The entire idea sounds too fantastic to believe. Some individuals who do not believe that acetaminophen could possibly causse autism are gate-keepers in academic venues (prestigious journal editors, academic departmental executives, etc.), which makes discussing and circulating this research difficult, slowing adoption or change.

  3. Caregivers who have administered the drug to children under 6 years of age can be emotionally compromised by the possibility that they injured a child, albeit unintentionally. Emotional compromise understandably makes the concept difficult to accept.  

  4. Some evidence I've personally encountered would suggest that pharmaceutical interests might be at play. The liability for acetaminophen-induced neurological injury is essentially infinite, with one in 36 children now having autism, half of those cases being severe. Review of the medical literature shows where mistakes were made in the medical system, resulting in the use of acetaminophen in the pediatric population. From that evidence, no apparent wrongdoing from industry is evident. At present, it is my opinion that, with the evidence so overwhelmingly strong, it would make sense for industry to avoid interference.

  5. The science has moved slowly for a variety of reasons, three of which are listed in this paragraph. First, it took a long time before somebody actually tried to see if acetaminophen was a problem. Forty years elapsed between the discovery of autism and the first paper which showed that acetaminophen (and not a vaccine) caused autism. The second problem was that when this first paper connecting acetaminophen and autism was published in 2008, it was largely ignored until about 5 years later, when the first studies in laboratory animals were published showing that the drug is not safe for neurodevelopment. These studies in laboratory animals were also largely ignored. Looking back at the literature, it appears that even the authors of those studies using laboratory animals were not overly concerned about their results.  Then, thirdly, a large database analysis completely and tragically confused the medical community about the safety of acetaminophen for reasons we have demonstrated entirely (The safety of pediatric use of acetaminophen (acetaminophen): a narrative review of direct and indirect evidence - PubMed ( The end result of these and other factors listed here is that the science has moved very, very slowly. 

  6. Part of the problem is that most people expect acetaminophen to be safe because of an anecdotal bias. The anecdotal bias effect happens when people assume that because we know lots of people that took acetaminophen without getting autism, it must be safe.

  7. Part of the problem is a consensus bias that acetaminophen is safe, which means that we tend to believe acetaminophen is safe if others around us believe it is safe.  Direct to consumer advertising via trusted sources of information has reinforced this and other biases in favor of acetaminophen safety.

  8. Part of the problem prior to 2022 was that acetaminophen was "known" to be safe based on the medical literature. Literally hundreds of papers in prestigious medical journals say that it is safe for babies and children when used as directed.  After we tracked down exactly what the error was and when and where the error crept into the system (Acetaminophen (acetaminophen) use in infants and children was never shown to be safe for neurodevelopment: a systematic review with citation tracking - PMC (, publishing papers became much, much faster for our group. In other words, we needed to prove that a problem existed before people would listen.

  9. Autism was discovered in the 1940s, long before acetaminophen was in use, which might lead people to assume that acetaminophen can’t be the cause of autism. In fact, drugs were in use long before 1940 which the body breaks down into acetaminophen and could easily result in acetaminophen exposure early in life: The Dangers of Acetaminophen for Neurodevelopment Outweigh Scant Evidence for Long-Term Benefits - PubMed ( 

  10. Another part of the problem is that the adverse neurological effects either (a) don't show up immediately, or (b) can be blamed on the reason for giving the drug. For example, the adverse neurodevelopmental effects of acetaminophen exposure during circumcision do not become apparent until months after the exposure, when behavior can be assessed. Since there is no way to measure behavior before and after circumcision in the first hours of life, the only way the problem was tracked down was to evaluate large groups of children with and without circumcision, then use deductive reasoning to determine why the circumcised children have so much more autism.

  11. It is possible that a tragic focus on an alleged role of vaccines in the pathogenesis of autism has partially derailed focus on the actual cause. The first connection between vaccines and autism was published in 1998. Although the finding that acetaminophen, not vaccines, was responsible for autism was published a decade later, in 2008, major public attention is still focused on vaccines in 2024 as judged by rhetoric in the current US presidential campaign.

  12. It is possible that a misguided focus on the role of acetaminophen exposure during pregnancy in the induction of autism caused some problems. The risk from exposure during pregnancy is apparently very minor compared to the risk of exposure of the neonate. With this in mind, a primary focus on pregnancy in the media and subsequently in lawsuits has drawn attention to data which are much less compelling than the overwhelming data pointing to problems with acetaminophen after birth.    

  13. The current approach to science used by almost all scientists can be a problem. The approach is called “reductionistic”, which means that scientists focus on the fine details of a problem. Since almost all of the science funding is directed toward looking at the fine details, then almost nobody with funding (and thus almost nobody with a job in science) is left to look at the big picture. As of 2024, almost all scientists in the field are following a “multifactorial model” of autism induction which allows each scientist to work on a small piece of the puzzle. The bottom line is that not many people are looking at the big picture.  

  14. Conflicts of interest within the scientific community may be a factor. If the vast majority of all cases of autism are caused by acetaminophen, it means that we now know how to prevent autism. This situation presents loss of credibility and possibly even employability for many scientists working in the field. (For example, almost no funding is available to study scurvy because we know how to prevent the problem.) This situation constitutes a conflict of interest as well as an emotional compromise for many scientists working in the field. 

  15. My team has known since 2016 that, based on available scientific evidence, the most likely scenario is that acetaminophen causes almost all cases of autism. During that time, I have interacted extensively with the media on this subject. My perception is that the media has exercised extreme caution before publicizing this information. I think it likely that they feel that mistakes were made in publicizing the now-disproven link between vaccines and autism, and that those mistakes led to a public health crisis and some injury, which has yet to be resolved. I believe that they do not want to repeat that mistake, and, with notable exceptions, have inadvertently and tragically erred on the side of caution. 


Despite these hurdles, I believe that the situation is very close to resolution. I believe that we will soon stop administering acetaminophen to children under age 6, and will reconsider exposure to the drug during pregnancy. The evidence is overwhelming, which helps tremendously. In combination with that evidence is the incredible bravery I have observed from specific individuals within the medical and scientific communities. This is a great example in which it only takes a few individuals to make a huge difference. 


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