New research shows that streptococcal infection does not appear to cause or trigger Tourette syndrome or obsessive-compulsive disorder (OCD). The research is published in the September 30, 2009, online issue of Neurology®, the medical journal of the American Academy of Neurology. "These results do not confirm other, smaller studies done in the US, which found an association between strep infection and these brain disorders," said study author Anette Schrag, MD, of the University College London in the United Kingdom. "Streptococcal infection has previously also been linked to other, much rarer neuropsychiatric disorders." OCD is an anxiety disorder characterized by unwanted thoughts or obsessions and repetitive behaviors. Tourette syndrome is a neurologic disorder characterized by repetitive, involuntary sounds and movements called tics. The study involved 255 people between the ages of two and 25 from a large, unselective population in the United Kingdom. Of those, 129 were diagnosed with OCD and 126 with Tourette syndrome or tics. Scientists compared the two groups with 4,519 people of similar ages without these disorders. In the group with OCD, 15 percent had been exposed to a possible strep infection within two years of diagnosis. There was a similar rate among the comparative group of people without OCD. In the group with Tourette syndrome or other tic disorders, 10 percent had been exposed to a possible strep infection within two years of diagnosis, similar to people without the disorder. Researchers also looked at possible strep infections within five years of diagnosis of a strep infection. The researchers found that people with OCD or Tourette syndrome and tics were no more likely to have had possible strep infections compared to people without these disorders at two years and five years. The study was supported by the Tourette Syndrome Association.