No, Tylenol Does Not Cause Autism

That’s not what the research says: there is no conclusive evidence proving a causal link

Popular media always gets it wrong

I was avoiding writing about this because I did not want to lend validity to the ridiculousness of these recent claims that Tylenol causes Autism.

Having recently been solicited by Autism Moms (TM), asking me to include information on my website warning parents of the “dangers” of taking Tylenol while pregnant, I could hold back no longer.

First of all, Autism is not dangerous. It’s a neurodevelopmental disability, but also a wonderful natural variation, which lends greater variety to the neurological diversity of human beings.

There are many strengths and positive factors about being Autistic, and many Autistics are sick and tired of having our neurotype characterized as a horrible, dangerous tragedy that should be avoided at all costs.

And I mean all costs.

Some of these risks include not safely treating one’s pain while pregnant, or not vaccinating one’s children for very preventable diseases because of some false claims made by a quack (now-former) doctor.

Foolishness — dangerous foolishness. This misinformation and fear-mongering are the real dangers, not Tylenol or vaccines, or whatever random thing people are going to try and blame next.

I’ll break down a couple of these poorly-designed studies, and highlight the most glaring confounding factor they’ve all missed and failed to account for in their research.

Avella-Garcia et al., 2016

• Followed 2644 mother-child pairs
• Over 40% of those mothers reported using acetaminophen
• The study found that increased acetaminophen use was correlated with increased Autism diagnoses in males, and increased ADHD symptoms in both males and females
• Correlation does not equal causation
• Just because boys whose mothers took acetaminophen while pregnant happened to have increased Autism diagnoses does not prove that acetaminophen caused Autism
• Perhaps the mothers themselves are neurodivergent (are Autistic and/or have ADHD), which is highly likely because of the extremely high heritability of both ADHD and Autism
• Autistics and people with ADHD also have higher incidence of numerous co-occurring conditions, many of which could cause pain (more on that coming up), which could lead neurodivergent mothers to take acetaminophen more often than neurotypical mothers

Bittker & Bell, 2020

• Based on an Internet survey among parents of 1515 children in the U.S.
• The study found that increased acetaminophen use was correlated with increased Autistic diagnoses in males, but not females
• Again, correlation does not equal causation
• Just because boys whose mothers took acetaminophen while pregnant happened to have increased Autism diagnoses does not prove that acetaminophen caused Autism
• The fact that a correlation between prenatal exposure to acetaminophen and Autism in females was not found may be due to the fact that females are much more likely to be under-diagnosed or misdiagnosed, and their Autism missed, especially in childhood

The authors of this study made a very bold (yet unfounded) concluding statement,

“The PAF associated with postnatal acetaminophen was estimated to be about 40% of the risk of ASD among male children in the US.” — Bittker & Bell

• Patient and parent-report data are not incredibly reliable, especially when parents are trying to remember back to when they were pregnant
• This study is much too weak to draw any kind of conclusion about causation at all, and it is very irresponsible of these researchers to over-state their results in this matter

Autism, ADHD, and pain

Autism and ADHD are highly heritable, meaning if a parent is Autistic or has ADHD, their children have a much higher likelihood of also being Autistic or having ADHD.

Autism and ADHD also have numerous co-occurring conditions; conditions which are more likely to occur in people who are Autistic and who have ADHD. Many of these can cause pain, which could lead people to take acetaminophen.

It has long been advised to avoid taking ibuprofen while pregnant, and doctors have recommended acetaminophen for pain. So people who experience pain more frequently are more likely to take acetaminophen while pregnant.

Therefore, parents who are Autistic or have ADHD, who also have co-occurring conditions which cause pain, are more likely to have neurodivergent children, and are also more likely to have taken acetaminophen during pregnancy.

It is extremely likely their children would have been born Autistic or with ADHD regardless, given the genetic component. Until researchers rule out this confounding variable, they cannot come to any well-founded conclusions about causation.

I’ll outline a few conditions which are highly co-occurring with Autism and ADHD, and explain how they increase one’s risk for experiencing pain.

Dyspraxia (DCD) and hypermobility disorders

• People with dyspraxia and hypermobility disorders experience increased chronic pain, and significantly increased risk of injury, especially to the joints and ligaments

Sensory Processing Disorder (SPD)

• People with hypersensitivities might experience increased headaches due to light and sound sensitivities, or increased physical pain due to heightened somatic sensitivities
• Research has revealed that some people with SPD have enhanced facilitation of pain-transmitting pathways along with preserved but delayed inhibitory pain modulation
• This means people with SPD literally experience pain more intensely than those without, and their bodies are slower to inhibit the perception of pain

Depression and anxiety

• Increased stress, including depression and anxiety, have been shown to cause inflammation in the body
• Chronic, long-term stress can lead to physical manifestations, including painful conditions such as fibromyalgia, IBS, migraines, and arthritis
• People with anxiety experience more frequent headaches, stomachaches, and other physiological symptoms

Correlation does not equal causation

I’m not saying go ahead and take boatloads of Tylenol while pregnant. If you have any concerns about any medications or health-related questions, please speak to a medical professional (I am not one).

What I am saying is before panicking and needlessly enduring pain while pregnant, or launching a lawsuit against pharmaceutical companies, take a step back and critically evaluate the quality of the research which has been done thus far.

(It’s not great, most of it’s not even good).

The bottom line is this.

Parents who are Autistic or have ADHD:

• Are more likely to also have conditions which cause pain
• Are more likely to have neurodivergent children, and
• Are also more likely to have taken acetaminophen during pregnancy

Their children very likely would have been born Autistic or with ADHD regardless, given the genetic component. Until researchers rule out this confounding variable (among others), they cannot come to any well-founded conclusions about causation.

© Jillian Enright, Neurodiversity MB

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References

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