Want to know what’s wrong with you?

The docTORS had never seen anything like it. During covid-19 lockdowns teenage girls across the world began jumping, hitting and shouting insults and non-sequiturs such as “beans” and “beetroot”. Some were rushed to emergency rooms; neurologists called it a “pandemic within a pandemic”. Parents suspected Tourette syndrome, which can manifest as repeated twitches. But it turned out these were not ordinary tics: they were TikTok tics.

The girls had spent hours watching #Tourette and #Tic videos online. In three weeks in March 2021 views of videos on TikTok with those hashtags rose by 7%, to a whopping 5.8bn. Some of the girls were imitating what they had seen online to fit in with friends. Others had what doctors dubbed “functional tics”: a neurological disorder brought on by stress. One paediatric neurologist who had witnessed the sudden spike in patients started researching the phenomenon and discovered that online influencers were more likely to post videos with extreme tics to rev up user engagement. Two-thirds of the most popular content creators were selling merchandise on their accounts, directly profiting from internet-addled users.

Commerce, entertainment and wellness are “colliding” online, with huge repercussions for well-being. A new book by Deborah Cohen, a British journalist and trained physician, argues that the internet has “hijacked our health”. On YouTube health videos have amassed more than 200bn views, and people now google medical questions hundreds of millions of times a day. AI will make the internet an even bigger part of wellness. A recent poll by Ipsos, a pollster, found that nearly 30% of British respondents get medical advice from large language models (LLMs). Already 40m people worldwide use ChatGPT for medical advice; a new feature can tailor responses based on users’ medical records and fitness-tracking apps.

The benefits are clear. A few swipes and taps offer answers to questions you might otherwise have to queue at the doctor for—or be too embarrassed to ask. Yet Dr Cohen is not convinced technological progress is making people healthier. She calls out “unfettered” online advertising on social media and a “wellness industrial complex” (comprising pharmaceuticals, tech, testing and supplement firms) to argue that “a global experiment in public health” is being conducted online, which “may be doing more harm than good”. For every doctor who posts about medicine, there are more life coaches, health podcasters and charlatans who spread quackery: dog dewormer to cure cancer or a coffee enema to “detox” your system.

The internet is changing health in three important ways. First, it is persuading people they are sick when they are not. Dr Cohen analyses the “explosion” of posts about attention-deficit hyperactivity disorder (ADHD) in recent years. ADHD is typically diagnosed in childhood, but between 2020 and 2023 there was a 400% increase in adults seeking diagnoses in Britain.

Online users (including your correspondent) are often targeted by videos that shine a light on “secret signs” to look out for in adulthood. Influencers in scrubs ask questions like: “Do you struggle to finish a book unless it’s something you’re interested in?” (Doesn’t everyone?) In 2023 an analysis of the most-watched ADHD videos on TikTok found that less than 50% accurately reflected the symptoms. But by pathologising ordinary behaviours, videos are more appealing and likely to go viral, which helps those who are selling ADHD tests and supplements.

That points to the second change: the internet has created a “wild west” of medical advertising. In nearly every country apart from America and New Zealand, it is illegal to push drugs to consumers. But online, adverts from regions with less regulation reach patients everywhere. Ads are not always easy to spot, either: some firms work with “patient influencers” who receive free drugs or payment in exchange for mentioning the company’s name in their testimonies.

Online content often targets the “worried well”: healthy people who are anxious about getting sick. It is often said that sex sells in marketing, but when it comes to health, anxiety does. Videos with titles like “This Common Food Is Feeding Your Cancer Cells” get millions of views. Or take testosterone replacement therapy, which has gone from a niche treatment to one lauded online as a “fountain of youth” and type of “masculine fulfilment”, used by people like Joe Rogan, a podcaster, and Robert F. Kennedy junior, an American vaccine sceptic-turned-top health official. Some online clinics and adverts obscure testosterone’s side-effects, which range from awful (infertility) to awfully ironic (testicles can shrink).

Firms that can offer “quick fixes” to health concerns are in rude health. Yet such claims are unfounded, Dr Cohen notes, because medicine “is a science of probabilities rather than certainties” with no blanket cures that work for everyone.

All this is making doctors’ jobs harder, which is Dr Cohen’s third point. Many patients turn up to appointments with evidence for their suspected condition, buttressed by hours of watching influencers’ testimonies online. Some bring along the results of bogus tests and dodgy scans from small, unregulated companies. Doctors must then order further screening tests and biopsies to rule out diseases, which may make patients more anxious and waste everyone’s time and resources.

“Bad Influence” is a fascinating and richly researched book, and an excellent guide for anyone who finds himself regularly googling their symptoms. Yet like an unhelpful doctor, it focuses on what is wrong without offering many solutions. Dr Cohen spends too many pages on “the commodification of our health” and too few on how digital medicine could be used to revolutionise bureaucratic health systems and improve efficiency.

She is also too uninterested in AI, devoting only a few paragraphs to LLMs. Admittedly technology has progressed since her book went to press: LLMs can now diagnose common diseases nearly as well as physicians and have even outperformed humans on medical exams. Yet AI also makes it harder to study the negative effects of digital health care, as conversations are private and impossible for outside researchers to monitor (unlike the trumpeted endorsements of influencers). Dr Cohen simply concludes that “We deserve good influence so we can take better care of ourselves and each other.” That seems so obvious that readers may find themselves wanting a second opinion. ■