There's a lot of talk about vaccines that use the preservative thimerosal and how they could relate to autism, but there's no evidence to support a connection, according to a new review published in the journal Pediatrics.

What the researchers wanted to know: Does thimerosal, a vaccine preservative that contains mercury, cause autism?

What they did: The researchers searched the National Library of Medicine's database of journal articles and the Cochrane Library for studies published between 1966 and 2004 on thimerosal, vaccines, mercury, autism, and other neurodevelopmental disorders. They went over each study in detail, checking out the methods the authors had used and examining their results.

What they found: Out of 12 studies on thimerosal and neurodevelopmental disorders, four found an association—but all four were by the same authors, used overlapping data sets, and had "critical methodologic flaws," say the authors of this review, making the data and interpretation useless. In contrast, the studies that found no association were generally well designed and well analyzed.

What the study means to you: The well-designed studies found no connection between thimerosal and autism, and studies that found a link were deeply flawed—so maybe there's no link. As the authors point out: "Autism research dollars are limited, and parents of autistic children deserve to see finances directed to where they will do the most good."

Caveats: Most of the studies that found no link were European, but children in the United States were probably exposed to more thimerosal, back when thimerosal-containing vaccines were still common in the United States.

Find out more: The Autism Society of America provides information, support groups and other resources on autism.

The Institute of Medicine examined thimerosal-containing vaccines and neurodevelopmental disorders.

Read the article: Parker, S. K., Schwartz, B., Todd, J., and L. K. Pickering. "Thimerosal-Containing Vaccines and Autistic Spectrum Disorder: A Critical Review of Published Original Data." Pediatrics. September 2004, Vol. 114, No. 3, pp. 793–804.

Abstract online: http://pediatrics.aappublications.org/