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July 5, 2005

New Group Health study finds association between common childhood infection and neurologic conditions

Seattle—A new study adds support to an increasing body of evidence that the common childhood bacterial infection known informally as strep throat is associated with an increased risk for some neurologic conditions that frequently start in childhood—Tourette’s syndrome (TS), obsessive-compulsive disorder (OCD) and tic disorder.

The study, conducted at the Group Health Center for Health Studies (CHS) in Seattle, is published in the July 5, 2005 edition of the journal Pediatrics, accessible online at www.pediatrics.org. It suggests that strep throat (streptococcal infection) doubles the risk for a first diagnosis of TS, OCD or tic disorder within three months after infection. Multiple infections appear to approximately triple the risk for a first diagnosis of these disorders within 12 months.

"There are likely a number of different causes for these conditions, which often show up first in childhood or adolescence," explained Robert L. Davis, MD, MPH, senior researcher at CHS and the study’s corresponding author. "Following a number of different leads from past research, we’ve found more tantalizing clues about possible connections between childhood infections and certain disorders. However, our findings certainly don’t suggest that there is any immediate need for a change in medical—or parental—practice."

Davis did not suggest that parents and physicians should be more worried. Nor did he suggest parents do anything differently if their child gets strep throat. "Right now, this is all still in the research stage," said Davis. "We still don’t know if treatment with common antibiotics helps prevent these neurologic conditions that might follow strep throat, or reduce their severity, or shorten their duration if they do occur."

These disorders are more common than previously appreciated. OCD affects 1-2 percent of school-age children, and transient tics can affect up to 10-25 percent of elementary school-age children. Some researchers suspect the body’s natural response to infection—the production of certain antibodies directed to parts of the brain—might be linked in some way to pediatric autoimmune neuropsychiatric disorders (PANDAS), including TS, OCD, and tic disorder.

"Although the presence of these antibodies is more frequent among children with tics or TS, there’s much we still don’t know," said Davis. "For example, why do millions of children get strep throat every year, but only a tiny fraction develop these disorders?"

Davis and other researchers think that a person’s genes may play a critical role. One theory is that the strep infection might serve as a trigger for symptoms in only those children who carry a particular gene or set of genes. "It’s a promising avenue for additional study," Davis said.

The study examined the medical records of 202 pediatric patients with TS, OCD or tic disorder at Group Health, occurring between 1992 and 1999. Children were more than twice as likely as a control group (who did not have the disorders) to have had at least one streptococcal infection in the three months before disease onset, and almost twice as likely to have had a least one streptococcal infection in the 12 months before onset. Incidence of the disorders was more than three times as common among patients who’d had two or more step infections in the year before onset.

Other study authors include Loren K. Mell, MD of the Pritsker School of Medicine, University of Chicago, and David Owens, MD, of the University of Washington School of Medicine.

About Group Health Center for Health Studies
Group Health is a consumer-governed, nonprofit health care system that coordinates care and coverage. Based in Seattle, Group Health and Group Health Options, Inc. serve nearly 550,000 members in Washington and Idaho. Group Health’s Center for Health Studies conducts research related to prevention, diagnosis, and treatment of major health problems. Group Health Center for Health Studies is funded primarily through government and private research grants.

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