Last month I wrote about 5 logical fallacies that are trending right now in the world of health, and there was a resounding request for round two. So here you have it!

But first: why should you care? Learning to identify logical fallacies is a form of prebunking. There are SO MANY false health claims on the internet, and chasing them down one by one is not possible. Instead, if you can learn to recognize these common errors in reasoning and manipulative patterns, you can be prepared to discern unreliable information when you encounter it in the wild.

And research has shown prebunking works: teaching people logical fallacies helps them discern what information is reliable, and what is not.

Alright, now to the fallacies.

Anecdotal fallacy

The anecdotal fallacy occurs when people use their limited personal experience to make sweeping conclusions. Our personal experiences are important, and they guide many of our decisions. But they also often give us incomplete information because they only reflect one experience or point of view. The error in reasoning occurs when a person assumes their limited experience provides complete information and is enough to make much broader conclusions.

Examples of this fallacy in action:

• My child didn’t get vaccinated and they’re fine! (anecdote) Vaccines aren’t really needed. (broader conclusion)
• I stopped eating bread and felt better (anecdote)—gluten is causing so much inflammation in the modern diet. (broader conclusion)
• I started taking this new supplement and have so much energy (anecdote)—it really works! (broader conclusion)

Appeal to emotion fallacy

The appeal to emotion fallacy tries to win an argument not by providing evidence, but by distracting people with strong, emotionally charged language or imagery to evoke feelings such as fear, anger, or sadness.

The image below is a great example. It was used to try to convince Americans that children in the U.S. receive too many vaccines. Instead of providing accurate data, the image triggers an emotional reaction by using images of lots of needles, which feels scary, and by showing the U.S. baby as unhappy (frowning).

This emotionally charged imagery distracts people from the fact that the message is inaccurate.

U.S. babies do not receive 72 injections, and the image creates a distorted view of immunization by emphasizing fear of needles while ignoring the benefits.

Emotion, by itself, isn’t inherently wrong or invalid, and it can be used appropriately in health messaging.

The error in reasoning occurs when emotion is used in place of a reasoned argument, or when it is used to distract from the fact that insufficient or inaccurate evidence has been provided (as was the case here).

Appeal to authority

The appeal to authority fallacy says that authority figures (experts) are always right.

But this is not always true; reality does not bend to the will or whims of experts. Right now I think this one is especially confusing, because the scientific community says “trust the experts!” but then when an expert says something a bit weird, they say “ignore them!”

In science, what ultimately matters is the quality of the data and analysis—not who is making the claim. Experts are often more reliable because they’re trained to evaluate evidence, which is why it usually makes sense to trust them.

But their credentials alone aren’t proof—people with MDs and PhDs have to provide data to back up what they’re saying. The error in reasoning comes from assuming that a person’s title or credentials alone are enough to say they are correct, without requiring they provide additional evidence to support their argument.

Examples of this fallacy in action:

• “Dr. Malone is the inventor of mRNA vaccines; he knows what he’s talking about!”
• “I’ve seen five doctors online recommend this supplement—it must work.”
• “A Harvard study showed Tylenol during pregnancy is linked to autism, it must be true!”

The appeal to authority fallacy in action.

Moving the goal posts fallacy

The moving the goalposts fallacy occurs when someone refuses to accept valid evidence supporting an argument and instead changes their demands.

This tactic makes it so an argument is never settled because the demands are constantly changing.

One of the most famous examples of this fallacy is the rumor around vaccines and autism.

Back in the 1990s, the original argument was the MMR vaccine may be linked to autism.

This was studied extensively, and no link was found. But instead of saying “oh that’s great!” the goalposts changed and the rumor lived on: next it was alleged it was actually thimerosal (a vaccine ingredient) that was causing autism. When studies found no link between thimerosal and autism, the demands shifted again.

This has happened over and over again for the last three decades, turning what was once a valid hypothesis into an unfalsifiable rumor that is designed to never die. When moving the goal posts is used, no amount of data is ever deemed “enough.”

See this video on YouTube, Instagram, or Facebook.

Straw man fallacy

The straw man fallacy occurs when someone misrepresents an argument to make it easier to attack.

Instead of engaging with what was actually said, they oversimplify or exaggerate it, making it sound more extreme or simplistic than it really is. This fake version (“the strawman”) is easier to knock down, creating the illusion of winning the argument. But in reality, the original point was never addressed.

Examples of this fallacy in action:

“You said vaccines are safe, but clearly they have side effects!”

• Real claim: “Safe” means the benefits of vaccines outweigh the risks, and serious side effects are very rare.
• Straw man version: “Safe” means no risks of any side effects whatsoever.

“Doctors just want you to take a pill for everything.”

• Real claim: Chronic health conditions are complex, and sometimes diet and exercise alone are the best approach, while other times medications may be needed.
• Straw man version: Doctors just want to push pills for conditions that are really caused by poor diet and lack of exercise.

Communication tips for talking about fallacies

Prebunking by teaching these logical fallacies can be an effective strategy for helping people recognize unreliable health information. Here are a few communication tips to keep in mind when sharing these with your communities.

1. The goal is not to make people feel stupid. EVERYONE uses and falls for these fallacies from time to time, and they are not a sign of lack of intelligence. The goal is to empower people to identify and resist manipulation tactics, not to make them feel stupid. In general, shame-based messaging does not work, and it won’t work here.
2. Don’t just name the fallacy, explain the reasoning error. Naming the fallacy alone likely won’t help—the goal is to help people understand for themselves why the reasoning doesn’t hold up, so they can be equipped to identify the flaw in the future.
3. Provide real-world examples when possible. Hypothetical examples can be useful, but real-world examples help people see and understand these manipulation tactics in the wild, setting them up to identify them in the future.

Stay tuned for part three of this series, where we’ll dive into other rhetorical tricks that are commonly used to spread false health information. Subscribe below to follow along!

A version of this post was originally published on You Can Know Things.

Kristen Panthagani, MD PhD, is completing a combined emergency medicine residency and research fellowship focusing on health literacy and communication. In her free time, she writes the newsletters You Can Know Things and The Public Health Roundup. Views expressed belong to KP, not her employer.

Your Local Epidemiologist (YLE) is founded and operated by Dr. Katelyn Jetelina, MPH PhD—an epidemiologist, wife. YLE reaches more than 425,000 people in over 132 countries with one goal: “Translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

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Sunscreen. Lightweight dresses. Bug spray. That one snack my youngest will actually eat on a plane. And two tablets (but without YouTube downloaded because my kids have meltdowns when I take it away).

I’m leaving for Costa Rica soon, but mid-packing, two things hit my inbox, and the timing felt almost poetic:

1. A landmark lawsuit against major social media platforms, like YouTube, with states arguing these companies knowingly engineered addictive products that harm children.
2. The 2026 World Happiness Report, with this year’s theme centered on social media. As I scrolled to find the U.S. (ranked 23, no surprise there), I noticed Costa Rica was #4. I also noticed this: they use just as much social media as we do.

The two emails don’t fit neatly together: one landed like relief, the other like a complication. Both can be true, and sitting with that might actually be a useful place to start. Boy, do I have questions, as both a mom and a scientist. A lot of parents do. But I wasn’t finding the level of detail and nuance I was looking for in high-level news articles.

So I went straight to one of the leading experts in this space. Dr. Jacqueline Nesi breaks down technology for kids on her Substack, and she was gracious enough to bring her expertise to the YLE community, too. Because, as she said, we’re all missing more from the headlines than we think.

Jacqueline, take it away…

What happened last week with the lawsuit?

For the first time, a social media company was held liable for harm caused by its product—not the content users posted, but the product’s design.

Platforms have long been shielded by Section 230, which protects them from liability for user-generated content. This case argued something different: that the features themselves caused harm. The companies will appeal, but if the verdict holds, the implications are enormous. Thousands of similar lawsuits are slated for trial this year, and mounting financial penalties could force real changes to how these products work.

Is this social media’s “Big Tobacco moment”?

Yes and no. The legal strategy rhymes: personal injury lawsuits uncovering evidence of deception, building toward larger class-action cases and eventual regulation.

But social media and cigarettes aren’t the same thing. Cigarettes cause clear, dose-dependent physical harm (i.e., there’s no safe way to smoke). Social media doesn’t work like that. The picture is far more complicated.

Does social media cause mental health problems?

The scientific community has substantial correlational evidence and some, but not much, causal evidence of harm. Studies that randomly assigned people to stop using social media show mixed results, depending on how long they stopped, whether they quit entirely or just reduced use, and what they were using it for. Natural experiments, like tracking mental health outcomes when Facebook arrived on different college campuses, do show increases in distress after introduction. But research still has a long way to go to get a clear answer.

For some kids, social media is clearly a contributing factor. A few years ago, I (Jacqueline) ran a study with adolescents experiencing suicidal thoughts in an inpatient hospital unit. Many of the patients I spoke to had complex histories of abuse, neglect, bullying, poverty, and other major stressors. Some of these patients used social media in totally benign, unremarkable ways. A few of them, though, were served with an endless feed of suicide-related posts and memes, some romanticizing or minimizing suicide. For those patients, it would be very hard to argue that social media did not contribute to their symptoms, even with everything else going on in their lives.

For the plaintiff in this case, is it possible that these social media platforms were one such factor? Yes.

But there’s a “but”?

Of course there is a but. Mental illness is idiosyncratic. Its causes differ between people, and for any one person, it is almost never the result of a single cause.

It is one thing to say that for some kids, social media is one factor contributing to mental health symptoms. It is another thing entirely to say that social media is causing mental health problems on a large scale. It is still the case that if you take an average, healthy teen and give them social media, this is highly unlikely to create a mental illness.

Are features like infinite scroll and auto-play addictive?

Many social media platforms are designed to keep people, including children, using them for long stretches. If a child is faced with infinite scroll (i.e., a feed that never ends), or auto-play (i.e., videos that automatically play, one after another), they are going to spend more time on a platform than they would if those features did not exist. These features are effective. A growing body of academic research suggests features like infinite scrolling, autoplay, and push notifications are engineered to make self-control difficult.

But, there is much debate in psychology about whether social media use (or, really, any non-substance-using behavior outside of gambling) can be called an “addiction.” There is no clear neurological or diagnostic criteria, like a blood test, to make this easy, so it’s up for debate:

• On one hand, some researchers argue that compulsive social media use shares enough features (loss of control, withdrawal-like symptoms, continued use despite harm) to warrant the diagnosis for treatment.
• Others say the evidence for true neurological dependency is still weak and inconsistent because research relies on self-reported data, findings haven’t been replicated, and many heavy users don’t show true clinical impairment without pre-existing issues.

Here’s my current take: There are a small number of people whose social media use is so extreme that it causes significant impairment in their lives, and they are unable to stop using it despite that impairment. And for those people, maybe addiction is the right word.

For the vast majority of people (and kids) using social media, though, I do not think addiction is the right word to use. Stepping back from that label allows us to:

1. Recognize the full picture: We can acknowledge the benefits teens report from social media, like staying connected with friends, meeting like-minded peers, and exploring their interests, instead of treating all use as inherently problematic.
2. Preserve agency: We can empower kids to develop healthy habits and self-regulation skills, rather than telling them they are powerless over their own behavior.
3. Drive systemic change: Preserving the precision of the addiction label—reserving it for the small number of kids whose use is genuinely compulsive and impairing—actually strengthens the case for platform accountability, rather than weakening it. It’s that targeted claim that has driven legal action and regulatory pressure. Expanding it to average use shifts focus from systemic design fixes to individual diagnosis, and dilutes the very argument that holds platforms responsible.

How does social media fit into the larger context?

Social media isn’t happening in a bubble; it is playing out within a larger societal landscape.

Take Costa Rica, for example. It doesn’t necessarily have fewer mental illnesses. And it certainly doesn’t have less social media use. What it has is a deep social fabric, and that may mean social media use reinforces real-world connections in Costa Rica, whereas in English-speaking countries, it may be replacing them.

In other words, cultural factors appear to be protective. The underlying challenges to social foundations—trust, connection, belonging, and safety—are what drive happiness. Friendships, being known by someone, the sense that you belong somewhere: these are the actual load-bearing pillars of mental health, more predictive of wellbeing than income, and more protective against mental illness than almost any intervention we have.

What does all of this mean for parents?

The risks of social media that we’ve long known about are the same, and so are the basics:

• If you know your teen is vulnerable, perhaps due to existing mental health challenges or social struggles, you may want to be extra careful.
• If your teen is using social media in moderation, and it does not seem to be affecting them negatively, it probably isn’t.
• For many families, it makes sense to delay introducing social media, and when you do, to go slow, with plenty of oversight.
• Have conversations, early and often, about the technologies in our pockets. Share the benefits and risks, and listen to your teen’s perspective, too.
• Consider limits to protect time for what matters, like social connection, sleep, and physical activity.

But when it comes to our kids’ mental health, it’s important to keep the whole picture in mind. Social media may be one piece of the puzzle, but it’s certainly not the whole thing.

Bottom line

This verdict is a crucial moment, legally and culturally. It’s a chance to return to what we already know: these products require caution, and we should be intentional about whether and how our kids use them.

But Costa Rica is a useful reminder that the goal was never zero social media. It was stronger foundations: real connection, real belonging, adults who show up. The verdict is a step toward making sure the products our kids use are built with that in mind.

It’s not enough on its own. But it’s a start, and so is the conversation.

Love, JN and YLE

Jacqueline Nesi, PhD, is a clinical psychologist, psychology professor at Brown, and mom of three. Subscribe to her newsletter Techno Sapiens for the latest research on living and parenting in the digital age.

A previous version of this was posted on Techno Sapiens here.

Your Local Epidemiologist (YLE) is founded and operated by Dr. Katelyn Jetelina, MPH PhD—an epidemiologist, wife, and mom of two little girls. YLE reaches over 425,000 people in over 132 countries with one goal: “Translate” the ever-evolving public health science so that people will be well-equipped to make evidence-based decisions. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below: