Calgary, Alberta—Exposure to the bacteria that causes strep throat appears to worsen some behavioral disorders, just not necessarily the ones assumed to be linked.

That’s according to an article in the journal Neurology. Canadian researchers from the University of Calgary and colleagues determined that a case of strep throat doesn’t seem to make Tourette syndrome and other chronic tic disorders worse in children and teens.

On the other hand, they found that exposure was associated with increased symptoms of hyperactivity and impulsiveness, such as those that occur with attention-deficit hyperactivity–disorder (ADHD). The authors point out that previous studies have suggested a possible link between strep infection and tic and behavioral disorders.

Background information in the article explains that tics are repetitive movements and vocalizations prompted by an irresistible urge to produce them. Those symptoms occur in disorders such as Tourette syndrome, which is a neurodevelopmental disorder that begins in childhood.

For the study, researchers focused on Group A Streptococcus (GAS), which causes strep throat, impetigo, and a variety of other infections.

“The link between streptococcus and tics in children is still a matter of intense debate,” said study author Davide Martino, MD, PhD, of the University of Calgary in Alberta. “We wanted to look at that question, as well as a possible link between strep and behavioral symptoms like obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD).”

To accomplish that, the study team sought to examine prospectively the association between GAS pharyngeal exposures and exacerbations of tics in a large multicenter population of youth with chronic tic disorders (CTD) across Europe.

In the study, 715 children with CTD (age 10.7±2.8 years, 76.8% boys) were recruited by 16 specialist clinics from nine countries and followed up for 16 months on average.

Researchers assessed tic, obsessive-compulsive symptom (OCS), and ADHD severity during four-monthly study visits and telephone interviews. Parents also kept dairies of symptoms.

In addition, GAS exposures were analyzed using four different combinations of measures involving pharyngeal swab and serological testing. The authors measured associations between GAS exposures and tic exacerbations or changes of tic, OC, and ADHD symptom severity.

Over the study period, 405 exacerbations occurred in 43% of participants, with the proportion of exacerbations temporally associated with GAS exposure ranging from 5.5% to 12.9%, depending on GAS exposure definition.

Results indicate no significant association of any of the four GAS exposure definitions with tic exacerbations (odds ratios ranging between 1.006 and 1.235, all P values >.3). GAS exposures were associated with longitudinal changes of hyperactivity-impulsivity symptom severity ranging from 17% to 21%, depending on GAS exposure definition, however.

“This study does not support GAS exposures as contributing factors for tic exacerbations in children with CTD,” the authors conclude. “Specific work-up or active management of GAS infections is unlikely to help modifying the course of tics in CTD and is therefore not recommended.”

“While our findings suggest that strep is not likely to be one of the main triggers for making tics worse, more research is needed into other possible explanations,” Dr. Martino added. “For example, the social stress of having this disorder could be implicated in making tics worse more than infections. It's also possible another pathogen might be triggering an immune response associated with tic worsening.”

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