Since 2008, when a group of physicians drew a hypothetical link between Lyme disease and autism, a growing number of patient activists have embraced the belief that the hallmark neuropsychiatric symptoms of autism may spring from the body's immune response to the bite of a deer tick carrying the bacterium Borrelia burgdorferi.
But a research letter published Tuesday in the Journal of the American Medical Assn. casts doubt on the link.
A group of researchers and clinicians from Weill Cornell Medical College and Columbia University Medical Center acquired blood samples and medical records of 120 children -- 70 of them diagnosed with autism and the rest unaffected siblings or healthy controls -- recruited primarily from the northeastern and western United States, where Lyme disease infection is relatively high. They tested that blood for signs of exposure to B burgdorferi.
Among the 70 patients with autism, one had positive antibodies to the bacterium, suggesting that child had probably been exposed to the bacterium that causes Lyme disease. The rate of exposure to B burgdorferi was higher among the study's 50 children unaffected by autism: four tested positive for antibodies to the pathogen.
Though a seemingly small group, a statistically significant finding in that sample size would give relatively high confidence that, were a relationship to exist, it would have been picked up.
The researchers acknowledged that this data did not address whether perhaps Lyme disease "may cause autism-like behavioral deficits in some cases." But they said the findings "effectively rule out" the suggestion that children with autism are themselves disproportionately infected by or exposed to the bacterium that causes Lyme disease.
That would seem to weaken one link in the chain of logic suggesting that autism may result from exposure to Lyme disease -- whether on the part of a pregnant woman or the child. The authors of the Medical Hypotheses article that touched off speculation about an autism-Lyme disease link cite studies showing that 20% to 30% of those with autism are positive for exposure to Lyme disease-causing bacteria.