Emily Oster

7 min Read Emily Oster

Emily Oster

Tylenol in Pregnancy and ADHD

Unpacking a new paper

Emily Oster

7 min Read

In April, 2024 a new paper was released which uses a much better approach to the data to address this question. That paper establishes there is no relationship between Tylenol exposure and ADHD or autism in children. Please read the post in this updated data here.

Several weeks ago, a new paper was released in the European Journal of Epidemiology about Tylenol in pregnancy and ADHD in children. It was greeted with the usual breathless terror in the media and, for me, with the usual swath of emails about what, if anything, it meant.

I’ll get into the details below, but the top-line claim in the paper is that children of mothers who take acetaminophen (the active ingredient in Tylenol) during pregnancy are more likely to show symptoms of, or be diagnosed with, autism or ADHD.

This brought back some memories for me. In 2014 I wrote for 538 about this precise question. The article came out very shortly after I was turned down for tenure at my last job, and a day or two later a senior colleague came in to give me some career advice. He asked me: “Do you really want to be a person who writes about things like whether pregnant women can take Tylenol?”

I cannot remember what I said at the time, but I guess subsequent events suggest the answer was “Yes”.

Anyway: here we are again. I’ll do a short overview of the paper, and then get into some analysis.

Short overview of a meta-analysis on Tylenol

This paper is a “meta-analysis”, meaning the authors combine results from a number of different studies. In their case, it’s six European studies in which mothers were asked about behavior during pregnancy (including whether they took acetaminophen) and their children were evaluated for Autism Spectrum Conditions (ASC) or Attention-Deficit/Hyperactivity Disorder (ADHD).

The authors aggregate the datasets and argue that exposure to acetaminophen during pregnancy is associated with an increased risk of both disorders. The increase is around 20% in both cases. Note this is 20 percent and not 20 percentage points. If the baseline risk of ADHD is 4%, then these results indicate taking acetaminophen during pregnancy would increase the risk from 4% to 5%.

The authors argue the results are more convincing for ADHD than for ASC, given the robustness checks they run, and are similar across boys and girls, although are slightly stronger for boys.

The paper concludes by suggesting additional caution is warranted by pregnant people considering taking Tylenol. The question is: how much do we believe these results?

My analysis

When I turn to analyze a paper like this, I tend to focus on two things. The first is how convincing the regression analysis is. The second — slightly more nebulous — is whether the aggregate picture makes sense.

Let’s start here with the first.

This paper is well done. It’s very clearly explained and the authors are transparent about what they are doing. There is a complementary analysis of maternal exposure to acetaminophen after pregnancy which doesn’t suggest a link with ADHD or ASC; this is a nice form of what we’d call a “placebo test”.

Having said this, the paper also has all the problems I spend my life complaining about. This isn’t a randomized trial and the characteristics of the mothers who take acetaminophen are very different from those who do not. The controls are imperfect. For example: they measure education as “Low”, “Medium” or “High”. But, of course, there is more variation than that in education levels and it seems very possible that this residual variation is driving some of the effect.

And some of the tests which are broadly convincing are less so when we narrow in. For example, in the largest dataset they use — the Danish National Birth Cohort (DNBC) — almost 60% of mothers take acetaminophen during pregnancy, but only about 10% after. This means the selection of acetaminophen-takers before and after is very different, making their tests harder to interpret.

Finally, there is the obvious issue of whether we can separate the impact of Tylenol from the impact of whatever people took the Tylenol for (for example, fever). That concern is basically impossible to address.

That’s the analysis of the regressions. Turning to the bigger picture…. The argument in the paper is that exposure to acetaminophen during pregnancy increases ADHD risk. If this is true, it follows that groups with overall more exposure should have higher ADHD rates, at least through this channel.

The paper makes use of six groups of mothers with varying rates of acetaminophen use. In the RHEA cohort, for example, only 14% of mothers are exposed during pregnancy, versus 56% in the DNBC. This variation allows us to ask, basically, how do the aggregate data line up with what we would predict based on the estimates in the paper.

Think about it this way: on average across groups (unweighted), 37% of mothers took acetaminophen and 7.6% of children were diagnosed with ADHD. The coefficients suggest that exposure increases risk by 20%. If we combine these facts we can predict the expected ADHD diagnosis rate in each cohort based on their acetaminophen exposure. And then we can compare this to the actual diagnosis rate.

These predicted-versus-actual numbers are shown in the graph below. They do not line up very well. For example: in the DNBC, this predicts 7.9% of children will have ADHD diagnoses, but the actual share in the data is 2.1%. On the other side, in the RHEA data we predict 7.3% but the actual share is 12.2%.

Another way to make this point, perhaps more simply, is just to note that the ADHD rates do not seem to closely relate to exposure rates. You can see this in the table below. The groups with the highest exposure actually have lower ADHD rates.

What to make of this? Does this mean that the regression results are wrong? No. But what it means is that if they are right, there must be significant offsetting factors. That is: these data predict that the DNBC cohort would have an ADHD rate of about 8%, when the actual rate is 2.1%. To reconcile this, we must think there is some other large factor (maybe multiple factors) which lower the ADHD rate in the DNBC, raise it in the RHEA, and so on.

Any model of the world which takes this 20% increase as correct must also include a story for why the aggregate facts do not align. If we find the size of the necessary other factors implausible, this is a reason to question the results.

(Side note: this idea relates closely to work by my husband and coauthors, in a paper entitled “Bounds on a Slope from Size Restrictions on Economic Shocks.” (Jesse also came up with the title “Cribsheet” so he is a title writer with very wide range). Effectively, I’m suggesting a much, much less math-y version of this argument from the paper: “Large fluctuations in ε_t may be plausible if the good in question is a particular brand of scarf, preferences for which may change radically from year to year due to advertising campaigns, changes in fashion, etc. Large fluctuations in ε_t may be less plausible if the good in question is a standard agricultural commodity, preferences for which are likely more stable.”)

Where does this leave us? When I write about questions like this, there is always the temptation to either be totally dismissive or to be convinced. This question falls, for me, in a grey area. I’m generally very skeptical of observational data, and I find the disconnect with the aggregate facts problematic. But the paper is not riddled with errors like the caffeine and pregnancy study I dismissed a few months ago. This area has enough attention and work that I hope — perhaps this is naïve — that at some point someone will bring a better research design to it. Until then, we are limited.

Toward the end of my second pregnancy I got a serious hamstring injury and couldn’t really walk. I took Tylenol, and I would do so again, trading what I see as a small possibility of a small risk against the benefits at the time. But this is a space — an uncomfortable one in some ways — in which reasonable people will make different choices.

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The list of what not to do while pregnant feels longer than a CVS receipt. At ParentData, we want to empower you to make the right decisions for you. 

What an amazing group of women, and an honor to speak at the #MomsFirstSummit debunking parenting myths. 

What are some pregnancy rules you chose to bend after being empowered by data?

#emilyoster #parentdata #pregnancyproblems #pregnancymyths

The list of what not to do while pregnant feels longer than a CVS receipt. At ParentData, we want to empower you to make the right decisions for you.

What an amazing group of women, and an honor to speak at the #MomsFirstSummit debunking parenting myths.

What are some pregnancy rules you chose to bend after being empowered by data?

#emilyoster #parentdata #pregnancyproblems #pregnancymyths
...

Looking for Memorial Day Weekend plans? Might be the perfect time to give potty training a shot. Potty training is notoriously difficult, and we unfortunately don’t have a lot of evidence-based guidance on what works best. So I asked the ParentData community to fill out a survey and share their knowledge — about 6,000 people responded.

👉Comment “Link” for a DM to an article that summarizes all of the best potty training advice we collected. 

Remember, you are not alone in the potty training struggle! It can be incredibly challenging, so please give yourself some grace.

#emilyoster #parentdata #pottytraining #pottytrainingtips #toddlertips

Looking for Memorial Day Weekend plans? Might be the perfect time to give potty training a shot. Potty training is notoriously difficult, and we unfortunately don’t have a lot of evidence-based guidance on what works best. So I asked the ParentData community to fill out a survey and share their knowledge — about 6,000 people responded.

👉Comment “Link” for a DM to an article that summarizes all of the best potty training advice we collected.

Remember, you are not alone in the potty training struggle! It can be incredibly challenging, so please give yourself some grace.

#emilyoster #parentdata #pottytraining #pottytrainingtips #toddlertips
...

We’re hiring an Associate Editor at ParentData! More details at my link in bio. Please share with the great writers and data-loving people in your network. 📊💻

We’re hiring an Associate Editor at ParentData! More details at my link in bio. Please share with the great writers and data-loving people in your network. 📊💻 ...

Do you brand things a certain way to get your kid to accept it? Like calling carrots “rabbit popsicles”? Or telling them to put on their “super speed socks” in the morning? Share your rebrands in the comments below! You never know who you might be helping out 👇

#emilyoster #funnytweets #relatabletweets #parentingjokes #kidssaythedarndestthings

Do you brand things a certain way to get your kid to accept it? Like calling carrots “rabbit popsicles”? Or telling them to put on their “super speed socks” in the morning? Share your rebrands in the comments below! You never know who you might be helping out 👇

#emilyoster #funnytweets #relatabletweets #parentingjokes #kidssaythedarndestthings
...

Have you ever panic-googled a parenting question when everyone else is asleep? If so, you’re not alone. 

Today is the first episode of a new biweekly series on my podcast: Late-Night Panic Google. On these mini-episodes, you’ll hear from some familiar names about the questions keeping them up at night, and how data can help. First up: @claireholt!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #emilyoster #claireholt #parentingstruggles #parentingtips #latenightpanicgoogle

Have you ever panic-googled a parenting question when everyone else is asleep? If so, you’re not alone.

Today is the first episode of a new biweekly series on my podcast: Late-Night Panic Google. On these mini-episodes, you’ll hear from some familiar names about the questions keeping them up at night, and how data can help. First up: @claireholt!

Listen and subscribe to ParentData with Emily Oster in your favorite podcast app 🎧

#parentdata #emilyoster #claireholt #parentingstruggles #parentingtips #latenightpanicgoogle
...

Sun safety is a must for all ages, especially babies! Here are my tips for keeping your littlest ones protected in the sunshine:
☀️ Most importantly, limit their time out in hot weather. (They get hotter than you do!)
☀️ Keep them in the shade as much as possible when you’re out.
☀️ Long-sleeve but lightweight clothing is your friend, especially on the beach, where even in the shade you can get sunlight reflecting off different surfaces.
☀️ If you want to add a little sunscreen on their hands and feet? Go for it! But be mindful as baby skin tends to more prone to irritation.

Comment “Link” for a DM to an article on the data around sun and heat exposure for babies.

#sunsafety #babysunscreen #babyhealth #parentdata #emilyoster

Sun safety is a must for all ages, especially babies! Here are my tips for keeping your littlest ones protected in the sunshine:
☀️ Most importantly, limit their time out in hot weather. (They get hotter than you do!)
☀️ Keep them in the shade as much as possible when you’re out.
☀️ Long-sleeve but lightweight clothing is your friend, especially on the beach, where even in the shade you can get sunlight reflecting off different surfaces.
☀️ If you want to add a little sunscreen on their hands and feet? Go for it! But be mindful as baby skin tends to more prone to irritation.

Comment “Link” for a DM to an article on the data around sun and heat exposure for babies.

#sunsafety #babysunscreen #babyhealth #parentdata #emilyoster
...

I’m calling on you today to share your story. I know that many of you have experienced complications during pregnancy, birth, or postpartum. It’s not something we want to talk about, but it’s important that we do. Not just for awareness, but to help people going through it feel a little less alone.

That’s why I’m asking you to post a story, photo, or reel this week with #MyUnexpectedStory and tag me. I’ll re-share as many as I can to amplify. Let’s fill our feeds with these important stories and lift each other up. Our voices can create change. And your story matters. 💙

#theunexpected #emilyoster #pregnancycomplications #pregnancystory

I’m calling on you today to share your story. I know that many of you have experienced complications during pregnancy, birth, or postpartum. It’s not something we want to talk about, but it’s important that we do. Not just for awareness, but to help people going through it feel a little less alone.

That’s why I’m asking you to post a story, photo, or reel this week with #MyUnexpectedStory and tag me. I’ll re-share as many as I can to amplify. Let’s fill our feeds with these important stories and lift each other up. Our voices can create change. And your story matters. 💙

#theunexpected #emilyoster #pregnancycomplications #pregnancystory
...

OUT NOW: My new book “The Unexpected: Navigating Pregnancy During and After Complications” is available on April 30th. All of my other books came out of my own experiences. I wrote them to answer questions I had, as a pregnant woman and then as a new parent. “The Unexpected” is a book not to answer my own questions but to answer yours. Specifically, to answer the thousands of questions I’ve gotten over the past decade from people whose pregnancies were more complicated than they had expected. This is for you. 💛 Order now at my link in bio!

OUT NOW: My new book “The Unexpected: Navigating Pregnancy During and After Complications” is available on April 30th. All of my other books came out of my own experiences. I wrote them to answer questions I had, as a pregnant woman and then as a new parent. “The Unexpected” is a book not to answer my own questions but to answer yours. Specifically, to answer the thousands of questions I’ve gotten over the past decade from people whose pregnancies were more complicated than they had expected. This is for you. 💛 Order now at my link in bio! ...

OUT NOW: My new book “The Unexpected: Navigating Pregnancy During and After Complications” is available on April 30th. All of my other books came out of my own experiences. I wrote them to answer questions I had, as a pregnant woman and then as a new parent. “The Unexpected” is a book not to answer my own questions but to answer yours. Specifically, to answer the thousands of questions I’ve gotten over the past decade from people whose pregnancies were more complicated than they had expected. This is for you. 💛 Order now at my link in bio!

OUT NOW: My new book “The Unexpected: Navigating Pregnancy During and After Complications” is available on April 30th. All of my other books came out of my own experiences. I wrote them to answer questions I had, as a pregnant woman and then as a new parent. “The Unexpected” is a book not to answer my own questions but to answer yours. Specifically, to answer the thousands of questions I’ve gotten over the past decade from people whose pregnancies were more complicated than they had expected. This is for you. 💛 Order now at my link in bio! ...

OUT NOW: My new book “The Unexpected: Navigating Pregnancy During and After Complications” is available on April 30th. All of my other books came out of my own experiences. I wrote them to answer questions I had, as a pregnant woman and then as a new parent. “The Unexpected” is a book not to answer my own questions but to answer yours. Specifically, to answer the thousands of questions I’ve gotten over the past decade from people whose pregnancies were more complicated than they had expected. This is for you. 💛 Order now at my link in bio!

OUT NOW: My new book “The Unexpected: Navigating Pregnancy During and After Complications” is available on April 30th. All of my other books came out of my own experiences. I wrote them to answer questions I had, as a pregnant woman and then as a new parent. “The Unexpected” is a book not to answer my own questions but to answer yours. Specifically, to answer the thousands of questions I’ve gotten over the past decade from people whose pregnancies were more complicated than they had expected. This is for you. 💛 Order now at my link in bio! ...

Is side sleeping important during pregnancy? Comment “Link” for a DM to an article on whether sleep position affects pregnancy outcomes.

Being pregnant makes you tired, and as time goes by, it gets increasingly hard to get comfortable. You were probably instructed to sleep on your side and not your back, but it turns out that advice is not based on very good data.

We now have much better data on this, and the bulk of the evidence seems to reject the link between sleep position and stillbirth or other negative outcomes. So go ahead and get some sleep however you are most comfortable. 💤

Sources:
📖 #ExpectingBetter pp. 160-163
📈 Robert M. Silver et al., “Prospective Evaluation of Maternal Sleep Position Through 30 Weeks of Gestation and Adverse Pregnancy Outcomes,” Obstetrics and Gynecology 134, no. 4 (2019): 667–76. 

#emilyoster #pregnancy #pregnancytips #sleepingposition #pregnantlife

Is side sleeping important during pregnancy? Comment “Link” for a DM to an article on whether sleep position affects pregnancy outcomes.

Being pregnant makes you tired, and as time goes by, it gets increasingly hard to get comfortable. You were probably instructed to sleep on your side and not your back, but it turns out that advice is not based on very good data.

We now have much better data on this, and the bulk of the evidence seems to reject the link between sleep position and stillbirth or other negative outcomes. So go ahead and get some sleep however you are most comfortable. 💤

Sources:
📖 #ExpectingBetter pp. 160-163
📈 Robert M. Silver et al., “Prospective Evaluation of Maternal Sleep Position Through 30 Weeks of Gestation and Adverse Pregnancy Outcomes,” Obstetrics and Gynecology 134, no. 4 (2019): 667–76.

#emilyoster #pregnancy #pregnancytips #sleepingposition #pregnantlife
...

My new book, “The Unexpected: Navigating Pregnancy During and After Complications” is available for preorder at the link in my bio!

I co-wrote #TheUnexpected with my friend and maternal fetal medicine specialist, Dr. Nathan Fox. The unfortunate reality is that about half of pregnancies include complications such as preeclampsia, miscarriage, preterm birth, and postpartum depression. Because these are things not talked about enough, it can not only be an isolating experience, but it can also make treatment harder to access.

The book lays out the data on recurrence and delves into treatment options shown to lower risk for these conditions in subsequent pregnancies. It also guides you through how to have productive conversations and make shared decisions with your doctor. I hope none of you need this book, but if you do, it’ll be here for you 💛

#pregnancy #pregnancycomplications #pregnancyjourney #preeclampsiaawareness #postpartumjourney #emilyoster

My new book, “The Unexpected: Navigating Pregnancy During and After Complications” is available for preorder at the link in my bio!

I co-wrote #TheUnexpected with my friend and maternal fetal medicine specialist, Dr. Nathan Fox. The unfortunate reality is that about half of pregnancies include complications such as preeclampsia, miscarriage, preterm birth, and postpartum depression. Because these are things not talked about enough, it can not only be an isolating experience, but it can also make treatment harder to access.

The book lays out the data on recurrence and delves into treatment options shown to lower risk for these conditions in subsequent pregnancies. It also guides you through how to have productive conversations and make shared decisions with your doctor. I hope none of you need this book, but if you do, it’ll be here for you 💛

#pregnancy #pregnancycomplications #pregnancyjourney #preeclampsiaawareness #postpartumjourney #emilyoster
...

We are better writers than influencers, I promise. Thanks to our kids for filming our unboxing videos. People make this look way too easy. 

Only two weeks until our book “The Unexpected” is here! Preorder at the link in my bio. 💙

We are better writers than influencers, I promise. Thanks to our kids for filming our unboxing videos. People make this look way too easy.

Only two weeks until our book “The Unexpected” is here! Preorder at the link in my bio. 💙
...