Why health advice on social media can quietly harm you

A doctor visit used to start with a symptom. Increasingly, it starts with a video. Journalist Deborah Cohen, author of the book Bad Influence, has spent years tracing how social media reshaped where people go for health information, and what that shift costs in unnecessary tests, anxiety, and real physical harm.

The wellness industrial complex

Cohen describes a shift from treating sick people to marketing to well people, a much larger and less regulated market. Tech companies, pharmaceutical brands, diagnostic testing firms, and supplement makers all compete for the same audience: people who feel fine but are told they might not be, underneath the surface. The logic is simple and old. Create the sense of a hidden problem, then sell the solution.

Regulators have historically focused on devices and drugs for sick people, leaving wellness products for well people in a much lighter regulatory zone. That gap is exactly where influencer marketing has grown fastest.

Why influencers feel more trustworthy than doctors

Health influencers build what researchers call parasocial relationships. Unlike a celebrity endorsement, an influencer talks to the camera like a friend, often from a car, a kitchen, or a bathroom mirror, and that intimacy builds trust quickly. Many share a hero's journey: they felt unwell, discovered a supplement or a device, and got better, implying viewers can too.

That trust matters because it flips a hierarchy that used to be stable. Randomized trials and meta-analyses once sat at the top of medical evidence, with anecdotes at the bottom. On social media, an anecdote can reach millions of views while a rigorous new trial gets a few hundred. Storytelling beats statistics, and uncertainty, which is central to real medicine, does not translate well into a short video.

When belief alone causes harm

The nocebo effect, where negative expectations produce real symptoms, shows up repeatedly in Cohen's reporting. During the pandemic, doctors across the UK, US, Canada, and Australia independently saw young women develop sudden Tourette's like tics, a pattern traced back to viral TikTok videos, some posted by influencers who were later found to be monetizing the symptoms through merchandise sales.

A similar dynamic played out with an at home hair strand test marketed for food intolerance testing. A woman with abdominal symptoms took the test, received a long list of foods to avoid, including healthy staples like bananas and cheese, and initially felt validated. She later suspected the improvement was a placebo effect. A UK study found that while about 20 percent of people believed they had a food intolerance, blinded testing confirmed it in fewer than 2 percent.

The hidden cost of screening

Full body MRI scanning, marketed heavily through celebrities and influencers, is one of the clearest examples of testing that no major medical body recommends for screening, and that some explicitly recommend against. Cohen documents a woman who paid thousands of dollars for a scan, was told by automated message that she had a brain lesion, and spent weeks in panic before a follow up scan at Prenuvo, the company that ran the original test, found nothing.

This is the pattern researchers call a clinical cascade: an initial test flags something ambiguous, which leads to more invasive follow up testing, which carries its own risk of complications, cost, and anxiety, often without changing the outcome. The same concern applies to newer full body scanning services like Neko Health, and to consumer screening more broadly. As one health system pattern shows, expanding screening for conditions like thyroid cancer increased treatment rates without reducing deaths, meaning more people were treated for disease that was never going to harm them.

How to evaluate health information you see online

• Ask why someone is on the platform. Are they selling something, even indirectly through affiliate links or sponsorships that are not clearly disclosed?
• Notice certainty. Real medicine is often uncertain and nuanced. Content that offers simple, absolute answers to complex health questions deserves extra scrutiny.
• Separate anecdote from evidence. A compelling personal story is not the same as a randomized trial, even when it has millions of views.
• Be cautious with screening tests marketed directly to consumers. Ask whether a professional medical body actually recommends the test, not just whether a company or an influencer promotes it.
• Check who is being paid. Physician and drug industry relationships face disclosure rules in many countries. Influencer marketing largely does not, so the absence of a disclosure does not mean there is no financial relationship.

The bottom line

Social media did not invent health misinformation, but it rewards certainty, emotion, and relatability over nuance and evidence, and that combination can turn ordinary anxiety into unnecessary tests, procedures, and real harm. A little skepticism about why content is being shown to you, and who benefits from you believing it, is one of the most protective habits you can build.