For 14-year-old Adrian it's "a curse". For Jenny, also 14, it means lying awake at night thinking "Why me?" The two teenagers have Tourette's syndrome, a neurological disorder characterised by physical and vocal tics.
The condition can cause misery for young people already struggling with adolescence, who find themselves bullied and mimicked at school - and who say they are often dismissed by teachers as naughty or disruptive.
The difficulties faced by secondary school students with Tourette's are explored in new research from the University of Nottingham in England. Academics carried out a series of interviews with 35 children suffering from the condition, as well as their parents, teachers and special educational needs (SEN) coordinators.
Although one in every 100 children has the disorder, many schools are failing to recognise it or offer support, the research suggests.
The children interviewed said that their physical tics made it hard to write by hand or complete homework, often causing them to feel anxious and angry. They added that teachers were frequently unaware of the condition and responded to verbal tics by telling them off. Students also reported being bullied by their peers, but said that few staff members were aware of this.
Many children did not tell their teachers that they had the disorder and spent so much energy trying to hide their tics - such as making unusual sounds or saying words out loud - that they were unable to concentrate on their work in class, the researchers found.
"When the tics are really bad I can't really concentrate on the work," one 13-year-old said. "I have to concentrate on keeping the tics in."
A 15-year-old boy explained that he held his tics in "but they build up and up, and then they have to come out".
After school, the children were often too exhausted to do homework. The mother of one teenage girl said: "She'd hold the tics in at school but then release it all at home. She just couldn't control them to do the homework... so we'd sit for three hours just to do a 30-minute piece of work."
The children interviewed said that they wanted staff and other students to "understand" and "ignore" their tics.
The syndrome - named after Georges Gilles de la Tourette, the French physician and neurologist who first described it - covers a wide spectrum, with tics varying greatly in frequency and severity. The condition is thought to be hereditary.
Georgina Jackson, the University of Nottingham professor of cognitive neuropsychology who led the research, said that the image of sufferers swearing randomly was misleading. Those suffering from "coprolalia" represented only a small proportion of people at the extreme end of the Tourette's spectrum, she said.
For most, the symptoms are milder. However, they still cause anxiety and stress and can have a profound effect on a child's experience and performance at school.
The involuntary tics usually start between the ages of 4 and 6 and peak between 11 and 14. In about 80 per cent of cases the tics become less frequent and less pronounced by the late teens. For the other 20 per cent of sufferers, the severe tics will continue into adulthood.
"Teachers can do much more to help pupils with Tourette's," Professor Jackson said. "Like all teenagers, they are keen to fit in and the quality of their school experience and friendships at this important stage of their life can have a huge impact on how they adjust to living with the condition in adulthood."
The results of the study are being used to devise a training package for secondary school staff to help them understand Tourette's and support students with the condition.
"Tourette's does not affect IQ or life expectancy. It's not a learning disability, although it can be a barrier to learning," Professor Jackson said. "With a bit of support these children can do very well at school."
Suzanne Dobson, chief executive of the UK charity Tourettes Action, which funded the research, said that teachers' lack of understanding could partly be explained by the "minuscule" amount of time devoted to SEN issues during teacher training.
She added that teachers needed to be aware that tics could be complex, and that children blurting out potentially insulting statements were not doing so intentionally.
"Teachers need the confidence in classroom management so that they can say to a class, 'Fred's got Tourette's. I will accept a certain level of things from him but I won't accept them from you, and I won't accept you going out of your way to provoke him'," she said.