Children who received general anesthesia repeatedly before the age of two had a doubling of their risk for learning disabilities at school age, according to a new study out Monday, the latest evidence that anesthesia could have a long-term impact on young children.

In recent years, a debate has intensified about the link between anesthetics and learning disabilities. Many animal studies have shown that the drugs hamper brain development when administered during sensitive growth periods, and a contentious human study published in 2009 -- by many of the same researchers who conducted this new research -- found an increased risk of learning disabilities for children who had anesthesia under the age of four.

The U.S. Food and Drug Administration (FDA) recently convened a meeting of experts to examine the evidence of anesthesia's effect on young children's brains, and concluded there was not enough data to advise parents about the risk. The agency has formed a partnership with the International Anesthesia Research Society called SmartTots to study the issue further.

One main question is whether the medical conditions for which the children need surgery -- and not the anesthesia during the surgery -- is responsible for the learning disability.

The study, published Monday in the journal Pediatrics, took into account a child's health and other risk factors for learning disabilities, but it was not designed to definitively determine whether general anesthesia or a medical condition caused the cognitive problems.

Researchers from the Mayo Clinic compared the medical and school records of 350 kids born in Rochester, Minn., who had undergone repeated procedures requiring general anesthesia before the age of two with 700 children who had not had anesthesia.

The study matched the two groups on factors known to raise the risk of learning disabilities, including gender, at how many weeks they were born, and education level of the mother. They also conducted a statistical analysis to take into account the child's general health status and examined achievement tests to assess learning disabilities.

Taking the research evidence as a whole, "the studies are concerning … but are in no way definitive," said Randall Flick, one of the study authors and chairman of the division of pediatric anesthesiology at Mayo.

There is not enough information yet to advise parents about any risk of learning disabilities, but parents with concerns should talk to their doctors, according to Flick, also an FDA advisory-panel member.

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