Billie Eillish has said that living with Tourette Syndrome is "very exhausting." 

The 20-year-old singer was filmed having a tic during an interview with David Letterman on the show My Next Guest, broadcast on Netflix.

"If you film me for a period of time, you will see several tics," she said. The disorder is manifested by involuntary sounds or movements- tics that can be motor or verbal.

This occurs due to a dysregulation of the mesolimbic circuit, a region of the brain that is

responsible for thoughts, emotions, and movements. The syndrome can also have a genetic origin.

The disorder usually begins in childhood, but tics and other symptoms usually improve over the years and in some cases disappear completely.

Billie said during the interview that she doesn't usually have tics when she

performs on stage and that some of them have disappeared over time, but others appear regularly.