A new study has found no evidence of an association between Lyme disease and autism.

Health experts previously thought some cases of autism might have been the body's immune response to the bite of a deer tick. The prevalence of Lyme disease in at least 20 percent of children with autism spectrum disorders has been reported.

However, new research shows no link between the two illnesses. The new study looked at blood samples and medical records of 120 children. About 70 of the children were diagnosed with autism and the rest were unaffected siblings or healthy control subjects. They tested that blood for signs of exposure to B burgdorferi, the bacterium carried by a deer tick that causes lyme disease, through a Centers for Disease Control approved method of testing.

Researchers say the findings "effectively rule out" the suggestion that children with autism are more often exposed to the bacterium that causes Lyme disease.

"We did the testing by the CDC-recommended two-tier testing and didn't find any of the children to be positive. Our sample size is large enough that these findings can rule out a high prevalence of Lyme disease in children with autism spectrum disorders," study senior author Armin Alaedini, an assistant professor of medical sciences in the department of medicine and the Institute of Human Nutrition at Columbia University Medical Center, in New York City told Healthday.

The study was published Tuesday in the Journal of the American Medical Asssociation.

Health experts have expressed concern that parents who believe lyme disease is the cause of autism may seek long-term, unnecessary antibiotic treatments for the developmental disorder.

"Unless a child has been diagnosed with Lyme disease or another infectious disease, our findings don't support the idea of putting autistic children on antibiotics," Alaedini added.

Lyme disease primarily occurs in the northeastern part of the country and is considered endemic to 13 states in the region.