Tics are uncontrollable movements and vocalizations triggered by a strong desire to do so. They are the distinguishing feature of chronic tic disorders such as Tourette syndrome, a neurodevelopmental illness that manifests itself in childhood.

“There has been much debate about whether the bacteria that causes strep throat, group A streptococcus, plays a role in the development of tic disorders, with previous research providing mixed results,” says study author Anette Eleonore Schrag.

This study looked at a group of children who were at a higher risk of developing tics because they had a first-degree relative with a tic disorder and found no link between strep exposure and the development of tics.

The study included 259 children between the ages of three and ten who did not have tics but had a parent or sibling with a chronic tic disease. At the outset and throughout the trial, these children were checked for strep infection, which was found using throat swabs, blood tests to detect antibodies that suggest a strep infection, or a combination of these procedures.

The patients were followed for an average of 1.6 years, with medical examinations every two months, either in person or over the phone. Parents were also required to keep a weekly journal and to report any signs of tics in their child as soon as feasible. Tic onset was defined as the occurrence of three or more days of sudden, uncontrollable movement or vocalization in a three-week period, which was always verified on examination.

61 kids (or 24 percent) developed tics over the course of the trial.

Researchers looked at the frequency of tic disorders in children who had strep and those who didn’t, and discovered no link between strep infection and the development of tics. There was still no link when adjusted for age, gender, and parental education level.

When researchers checked up with the children two years after the study ended, they discovered that seven more kids had developed tics, but there was no link between tics and strep.

Independent of strep, scientists discovered a clear link between sex and the beginning of tics, with girls having a 60 percent lower probability of developing tics than boys, which is consistent with prior research findings.

The author said, “Future studies are needed to investigate whether pathogens other than strep, or other factors that affect the immune system, play a specific role in the development of tics.”

One limitation of the research is that subjects were enrolled at multiple research centers across Europe, rather than at a single site, which may have resulted in minor variations in participant assessment.                                                

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