Peter Snaterse/Shutterstock.
Peter Snaterse/Shutterstock.

A recent Channel 4 TV programme, Britain's Tourette Mystery – Scarlett Moffatt Investigates, promised to explain why there has been an increase in the number of people, mainly teenage girls, who have developed tics since the start of the pandemic.

The programme featured Echo, an 11-year-old who suddenly developed tics on the first day of school, just after she had fallen out with her best friend. Overnight she was "jumping, twirling, clapping, making noises". She has tics that involve hitting her mother and involuntarily calling her a "stupid motherfucker". She describes herself as having "sudden-onset Tourette's". After moving to a new school, within a few months, her tics stopped.

Nicole developed similar tics and took to social media with her mother to find out more and later to raise awareness. She acknowledged that watching other people tic can make her symptoms worse – but also that people are entertained by her social media posts. Her tics have not improved. She feels her tics are "who I am now".

In my work as a consultant neurologist, I've met people like Echo and Nicole, with sudden onset tics as a teenager. There has been an increase in numbers since the pandemic, but there is no mystery about what they have.

Functional neurological disorder (FND)

New tics in a teenager are hardly ever caused by Tourette's. Usually, they are "functional tics" (involuntary rapid and repetitive movement and sound), which are one of many possible symptoms of functional neurological disorder (FND).

FND is the second commonest reason for a visit to a neurologist and a hidden cause of symptoms like limb weakness, tremor and seizures. It sits at the interface between neurology and psychiatry.

FND explained.

FND can't be identified using conventional scans or tests. In the past, such symptoms have been stigmatised under labels like "hysteria" or "psychosomatic". Patients have often been disbelieved by health professionals – which is one reason they have remained so hidden.

Doctors have traditionally diagnosed FND when they couldn't find any other condition or tests were normal. That is dangerous and wrong.

FND is a "rule in" diagnosis that should be considered when there are specific features of the movement or seizure. A tremor that disappears when the patient is distracted, or leg weakness that improves when the doctor uses techniques (such as the hip abductor sign – shown below) that bring out automatic instead of voluntary movement, are all examples of diagnostic clinical signs of FND. They show that the "hardware" of the brain is fine, but the "software" has gone wrong.

Hip abductor sign.Differences from Tourette's

Functional tics are different from Tourette's tics in several ways.

Tourette's is a developmental disorder that begins gradually in early childhood. It is more common in boys. Functional tics typically start rapidly and are much more common in girls – although girls do get Tourette's, too.

Functional tics can involve movements, like Echo's, that hurt the person who has them, or others, whereas this is rare in Tourette's.

Coprolalia, the medical word for the kind of swearing vocal tic seen in the TV show, is rare in Tourette's, and much more common and frequent in functional tics.

People with functional tics often develop other types of FND. Nicole, featured in the programme, has FND-related collapses and functional dystonia (uncontrollable muscle spasms), which she has also featured on TikTok.

Tic diagnoses require expertise. People with Tourette syndrome have normal scans, and can usually suppress their tics to some extent, which can be distractible too. Many people with functional tics have a history of mild simple tics when younger. Some clearly have both Tourette's and FND.

Possible causes

Where there is some mystery is exactly why some people get functional tics, although we don't exactly know why people get Tourette's syndrome either. Since the time of Sigmund Freud, the blame has been placed on stress or psychological conflicts. These days, we still recognise the role of stress in making people vulnerable to FND, and in triggering it.

But we've also learned that things are more complicated than this. FND can occur without stress being a trigger. Sometimes it arises as a result of an injury, an illness or even a transient vaccine reaction.

We've also learned something that was frankly obvious all along. FND arises from a problem in the brain, as revealed by modern functional neuroimaging and other techniques, in ways that are different to people pretending similar symptoms. But really, what other organ did anyone expect it would come from?

So what about the rise in functional tics? There is a recorded rise, but this is not an epidemic. Functional tics have been recognised for decades and the recent examples recorded in scientific papers since the pandemic only amount to a few hundred cases. The latest word from the clinics, including my own, is that numbers are now falling.

Role of social media

Social media, including TikTok, has been blamed by some researchers. We already know that people who tic are more likely to do so by watching others with the same thing. This is similar to how watching someone yawn makes you yawn or feel sleepy. But can watching someone tic induce a brand new tic disorder? For functional tics, in some cases, yes, but not for Tourette's, which is a developmental condition.

The number of teenagers whose tics were recorded as being influenced by social media in studies ranges from 20% to 100%. But how many teenagers are not influenced by social media? And isn't it understandable that when a teenager looks at videos of tics that they might start to experience one?

There are cases where "social contagion", such as clustering of cases in schools or among friends, is persuasive. But suggesting that social media is "the cause" of functional tics, rather than one of many potential risk factors, is not plausible to me.

FND rarely has one cause. It would be like blaming all cases of stroke on smoking. Sure, smoking is relevant for some, but so are lots of other things - genetics, cholesterol, hypertension and bad luck.

Better recognition needed

Scarlett Moffatt comes across as sincere on her programme. She had tics herself when she was 11, which she linked to anxiety and her dad's cancer diagnosis. She talked about the difficulties of lockdown for teenagers and how social media can be both helpful and harmful for people with tics.

However, the programme didn't discuss FND and caused upset among people with Tourette's by suggesting wrongly that it could be acquired by watching too much social media. Tourette Action the leading UK charity subsequently put out a statement along with FND charities, FND Hope and FND Action.

Everyone loves a mystery, but this is one where the answer, FND, deserves better recognition. The reason it has languished so long in the shadows is perhaps a much more interesting mystery.

Jon Stone receives funding from Chief Scientist Office Scotland. He is medical advisor to FND Hope and FND Action. He is Secretary of the FND society and runs a free self help website for people with FND, neurosymptoms.org. He carries out expert witness work in relation to FND