Correlation ≠ Causation
Tylenol and Autism- What the Science Says. Why Two Things Happening Together Doesn’t Mean One Caused the Other
Here’s a fun fact: ice cream sales go up at the same time as shark attacks. 🍦🦈 Does that mean eating ice cream causes shark attacks? Definitely not — it just means both happen more often in the summer. That’s what we call correlation — two things happening together — but it’s not the same as causation, where one thing directly causes the other.
This mix-up shows up everywhere in health research. For example: 👉 “Kids who eat more sugary cereal are more likely to struggle in school.” Sure, those two things might happen together, but that doesn’t mean the cereal is to blame. Maybe kids with busier mornings skip protein-rich breakfasts, or maybe other lifestyle factors are involved.
This is a hot topic right now and causing a lot of confusion. There have been studies that have shown correlation between acetaminophen (Tylenol) use and autism— but that’s not proof of causation. It could be that families who use Tylenol are also dealing with fevers, infections, or other health conditions that actually influence risk. The science isn’t settled, and more research is needed before we draw any conclusions.
The real story is probably much more complex. What we do know is that there seems to be a complex interaction between genetics and environment that leads to autism. There are some well-established risk factors including age of parents (older moms and dads increase the risk), high blood sugar or high blood pressure in pregnancy, exposure to a some types of anti-seizure medications, pregnancies less than 12 months apart, and complications at birth. We have seen large scale studies that have refuted the claim that vaccines cause autism. There are hundreds of different genes that have been associated with autism and each of those may be affected by different factors as well. Human bodies are complex and often the cause of disease is a complex interaction between lifestyle, environmental exposures and genetics.
An article published in the Journal of the American Medical Association in 2024 found no increase in the risk of autism related to Tylenol use. This study evaluated more than 185,000 children. (That is a huge sample of children for any medical study!) Not only was it a large study but it compared risk among siblings which have very similar lifestyle and exposures and still found no significant correlation between Tylenol use and pregnancy. For those interested, you can read the report here. (We’ve provided the citation at the bottom of this as well.)
Bottom line: Correlation gives scientists a clue, but causation is the real answer — and it usually takes a lot of research to prove. So before panicking over a headline (or blaming your ice cream habit for shark attacks 🦈🍨), consider what research is being discussed. Often it takes many studies to gather the data needed for scientists to truly understand what factors influence disease.
References:
Ahlqvist VH, Sjöqvist H, Dalman C, et al. Acetaminophen Use During Pregnancy and Children’s Risk of Autism, ADHD, and Intellectual Disability. JAMA. 2024;331(14):1205–1214. doi:10.1001/jama.2024.3172