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When I say Tourette's, you might picture someone swearing, like, explosively. Like, fountains of colorful four letter words, in response to…like, nothing.

This is called coprolalia, which comes from the Greek words that mean “poop” and “talk,” which I guess is fitting. And it's one of the most obvious symptoms of Tourette's, but it is not the most common one. This disorder is a lot more complex than people might think, and scientists are still trying to understand what's going on in the brain to cause it.

The DSM-V classifies Tourette syndrome, also known as Tourette's disorder, as a neurodevelopmental motor disorder. It was named after the French neurologist who first described it in a patient. To be diagnosed with Tourette's, people need to experience two or more motor or verbal tics— a sudden, quick movement or vocalization.

Tourette's is described as having these tics multiple times daily, consistently or intermittently for at least a year. And there are other diagnoses for fewer tics or different patterns over time. More often than not, tics are described as being extremely uncomfortable or impossible to resist.

Think of being told to, like, hold in a sneeze, but instead of sneezing, you're saying something pretty mean about your friend's cat. These verbal tics aren't always swears though. They could be repetitions of words that other people say, or sounds from nearby, known as echolalia.

And similar to verbal tics, motor tics can be vulgar or echo the movements of others. They can also be just a movement with no reason behind it, like someone smacking their own forehead or having an uncomfortable facial twitch. In some people diagnosed with Tourette's, these verbal and motor tics can be quite dramatic— like hitting or yelling at inappropriate moments.

But many people's tics are so small that they might not even realize they have Tourette's. They can fly under the radar for diagnosis their whole lives. Some estimates say that around 1 in 100 to 1 in 1000 people worldwide may suffer from Tourette's.

A study of 3500 patients in 22 countries suggested that men are 4.3 times more likely than women to be given the diagnosis. The average age of onset is thought to be around 6 years old, and research from the Yale Child Study Center that followed 36 young patients throughout their childhood placed the peak of tic severity at around age 10. By the age of 18, nearly half of the patients involved in that study were basically tic free.

But even though it's more common for children to be diagnosed with Tourette's and grow out of it, many adults suffer from it, and can experience their first symptoms later in life. It's also worth mentioning that people diagnosed with Tourette's more often than not have comorbidities. In that same study of 3500 people, only about 12% didn't.

Comorbid disorders are those that commonly occur alongside it, like Attention Deficit Hyperactivity Disorder or Obsessive-Compulsive Disorder. Now, Tourette's is a pretty intrusive illness to have when it comes to everyday life. A study from Canada conducted in the 1980s found that 40% of respondents had problems with dating, making friends, and keeping either kind of relationship.

So, besides trying to spread awareness of symptoms, psychologists have been trying to figure out what makes people tic. Biologically, we know that Tourette's has a strong genetic component, meaning parents have a chance of passing it on to their children. But we're not exactly sure what genes are involved.

But research has also shown that around a third of patients didn't inherit the disorder. And several cases have shown Tourette's surfacing after head trauma. Right now, scientists aren't too sure exactly what happens in the brain to cause Tourette's.

Many resources point toward dysfunction in the basal ganglia, which is a brain region responsible for voluntary movements, and areas in the frontal lobe that are responsible for impulse control. But there are a lot of structural and functional differences across the whole brain in patients with Tourette's. So it's hard to pinpoint what networks are really to blame.

To study what happens in the brain when tics occur, some researchers have used fMRI machines to analyze participants with the disorder. In one 2014 paper, for instance, scientists observed a wide range of active brain areas in the seconds leading up to a motor or verbal tic. Around two seconds before it happened, several areas in the cortex activated, which are toward the outer part of the brain.

Then, at T-minus one second to the tic, a bunch of regions deeper in the brain activated. Like the putamen, the amygdala, and the cerebellum… just to name a few of many. These various regions are involved in all kinds of things, from receiving stimuli, to processing information, to sending movement signals.

So the researchers analyzed the timings of these activations, and compared them to other ideas about brain networks. And they concluded that Tourette's patients may have an abnormality in the resting state network— a system made of many brain areas working together at a particular rhythm while your brain is just doing its normal thing. They suggested that something abnormal in this network might nudge the supplementary motor area, which is a key part of motor control in the cortex, into generating tics.

This nudge could potentially spread to linked motor areas, resulting in a really strong urge to move or vocalize. But this is far from the only hypothesis, and it doesn't have a way to explain what might cause someone's resting state network to become a bit wobbly. Different studies have noted changes in a lot of different brain areas.

So it may be some time before we have a definitive answer as to what causes Tourette's in the brain. But we do have a lot of information coming in, and we're narrowing it down a little bit at a time. And, who knows, maybe in a couple years we'll be able to make another video with some new updates.

Thank you for watching this episode of SciShow Psych! If you want to keep learning about different disorders with humans, you can check out the video hosted by Brit about Cotard's Syndrome, which is where people believe that they are dead. [OUTRO ♪].