Do you consult Dr Google when you feel unwell? Nearly 90 per cent of us do, according to a 2019 YouGov survey. It’s no bad thing that medical information is now readily accessible. There’s even a chance you’ll spot something your doctors have missed. But there are also obvious drawbacks: you might misdiagnose yourself, or notice problems with your health that didn’t bother you in the first place.
Particularly since the pandemic there have been claims of physical and mental health symptoms spreading via the internet – TikTok-inspired tics, among others. But is this even possible? And how widespread is it really?
Throughout history and across cultures, there are reports of physical symptoms spread solely via social transmission, particularly in the context of stress alongside close social affiliation. When 13 million Koreans were vaccinated during an influenza outbreak (2009-2010), a small proportion developed physical reactions (nausea, headaches, hyperventilation) without identifiable causes. This is an example of a “nocebo” effect – the antithesis of the placebo effect, when someone’s expectations about a treatment induce negative outcomes.
Which brings us to “TikTok tic”’. Since early 2020, some experts attribute a rise in tics – sudden, involuntary muscular contractions or vocal features – to teens watching YouTube or TikTok videos featuring influencers with Tourette’s syndrome. These channels are popular: #tourettes has 9.2 billion views. These have undoubtedly increased awareness about a rare neurological disorder.
One unforeseen consequence, however, may have been some degree of social transmission to vulnerable populations. Many clinicians have reported a huge rise in patients with “functional” tics, which appear noticeably different from typical Tourette’s tics, such as more arm movements, and fewer facial tics. In clinics across the world, most of these new cases of functional tic disorders had watched tic videos previously. The tics themselves can even mirror those of online influencers.
Some experts called this rise in tics a mass social media-induced illness. Others are more cautious: social media might be just one of many factors causing these new cases. In favour of the more balanced view, most people exposed to “TikTok tics” will not develop tics themselves. But social transmission likely plays a role in the minority who do, particularly in combination with other vulnerabilities such as stress.
Although distinct from tics caused by Tourette’s, TikTok tics are still “real” – they are not faked. Crucially, they have biological (as well as social) causes. Functional tics are likely mediated via changes in specific brain networks, particularly those supporting attention, expectations, and someone’s sense of agency over their body.
For instance, the brain might “learn” to associate certain environments with physical symptoms, and eventually trigger physical symptoms purely via expectation. This is possible because your brain sends information within itself and to the spinal cord about the physical state of your body, informing, adjusting, and sometimes radically changing your physical experience.
A similar phenomenon has been described in mental health symptoms. Dr Lucy Foulkes, of the University of Oxford, has suggested that increased mental health awareness via the internet might have both positive and negative consequences. In addition to helping people identify causes of their distress and seek appropriate treatment, awareness efforts could lead some individuals to “overpathologise”, or misidentify the causes of their distress as rare conditions such as dissociative identity disorder (previously multiple personality disorder; the hashtag #did has over three billion views on TikTok).
This mislabelling could in some cases even worsen symptoms and distress. “This represents a new route to the age-old phenomenon of social influence,” says Dr Foulkes.
“TikTok tics” are not the first phenomenon to be attributed to internet transmission, and they won’t be the last. It is not specific to social media, either: in my book, I write about the disorder Morgellon’s disease, coined in 2002 to describe an apparent skin infestation, and subsequently disseminated widely online. After hearing about Morgellon’s, many people reported they too had characteristic symptoms, including extreme itchiness and fibres emerging from skin lesions. But every large, robust study conducted on Morgellon’s to date has found the symptoms are not driven by parasites or bacteria. The best guess of scientists is that it is driven by something called “delusional infestation“: when someone is convinced they have an infestation, a conviction so intense that it can drive itchiness and other symptoms in and of itself.
The origins of online symptom spread are more complicated than they first appear. They are not “faked” or exaggerated, but mediated by brain mechanisms supporting learning about the world. Because much of our world is digital, the internet broadens and diversifies the environments we learn from – for better and for worse.
Camilla Nord leads the mental health neuroscience lab at the University of Cambridge. Her book, The Balanced Brain: The Science of Mental Health, will be published on 14 September
