Singer-songwriter Billie Eilish is raising awareness about Tourette’s syndrome after experiencing a head tic during a recent interview with comedian David Letterman on his Netflix series "My Next Guest Needs No Introduction."  

"What’s funny is so many people have it that you would never know," Eilish said.  

"A couple artists came forward and said, ‘I’ve actually always had Tourette’s,’ and I’m not gonna out them because they don’t wanna talk about it, but that was actually really interesting to me." 

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), the common diagnostic manual of psychiatrists, uses the same criteria for Tourette’s that the French neurologist Gilles de la Tourette used more than 100 years ago, defining a tic as a "sudden, rapid, recurrent, nonrhythmic motor movement or vocalization."  

Hayley Williams and Billie Eilish perform

(L-R) Hayley Williams and Billie Eilish perform on the Coachella stage during the 2022 Coachella Valley Music And Arts Festival on April 23, 2022, in Indio, California. (Photo by Amy Sussman/Getty Images for Coachella)

"Tourette syndrome is a neurological disruption that mostly affects school-age children. It is characterized by short, sudden physical movements as well as vocal outbursts. These symptoms usually abate over time, becoming less frequent after a child goes through puberty," the American Psychiatric Association (APA) said. 

Unlike other disorders in DSM-5, there is no severity threshold or impairment in daily activities criteria and the tic may last less than one year or become chronic by lasting over a year.  

Tics are like having hiccups -- even though you want to stop, your body continues to do it. Although sometimes people can briefly stop themselves from having a tic, eventually the person will do it, per the Centers for Disease Control and Prevention (CDC). 

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The tics are defined as motor or vocal, or a combination of the two, per the APA. 

Motor tics include blinking, shrugging the shoulders or arm jerking, whereas vocal tics include humming, clearing the throat or yelling out a word or a phrase per the CDC. 

But even though the syndrome is often portrayed in the media as shouting out swear words or constantly repeating words, these symptoms are not common or required for the diagnosis, per the agency. 

Billie Eilish accepts the Film Song of the Year award onstage during Variety's Hitmakers Brunch presented by Peacock | Girls5eva on December 04, 2021 in Downtown Los Angeles

Billie Eilish accepts the Film Song of the Year award onstage during Variety's Hitmakers Brunch presented by Peacock | Girls5eva on December 04, 2021, in Downtown Los Angeles. (Photo by Michael Kovac/Getty Images for Variety)

There is no single test to diagnose the condition, so healthcare professionals often go over a patient’s symptoms to see if they meet criteria for the syndrome.  

"When motor and vocal tics have been present and persisted at least a year, the term Tourette’s disorder is used," the psychiatric association said. 

Eilish, who is now 20, was diagnosed with the condition at age 11, but gets frustrated when people respond in an insensitive way because they don’t know she has it. 

During the interview with Letterman, she suddenly jerked her head, so he asked: "What’s going on? The fly?" 

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But she revealed she had just suffered a motor tic because of the lights in the room.  

"It’s really weird, I haven’t talked about it at all," Eilish replied when Letterman asked if she could talk about her experience with Tourette’s.  

"The most common way that people react is they laugh because they think I’m trying to be funny. They think I’m going [imitates tic] as a funny move. And so they go, ‘Ha,’ and I’m always left incredibly offended by that. Or they go [looks around] ‘What?’ and then I go, ‘I have Tourette’s.'" 

Billie Eilish attends Hitmakers Brunch

Billie Eilish attends Variety's Hitmakers Brunch presented by Peacock. (Photo by Kevin Winter/Getty Images for Variety)

When she was first diagnosed, she told Letterman she had small motor tics, involving her eyes or jaw, but she doesn’t know what causes them. 

As she got older, her tics progressed to wiggling her ear, raising her eyebrows, clicking her jaw or flexing her arms or certain muscles.  

"These are things you would never notice if you’re just having a conversation with me, but for me, they’re very exhausting," she said. 

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 But when she’s performing, focusing, riding her horse or moving around, she doesn’t experience any tics. She has "made friends with it." 

"I really love answering questions about it because it’s very, very interesting, and I am incredibly confused by it," Eilish said. "I don’t get it."