Young children with multiple exposures to anesthesia have had increased rates of ADHD, new research has revealed.

Researchers from the Mayo Clinic in Minnesota have done a retrospective study on children who had been exposed to anesthesia at an early age.  They found that for those children who were given anesthetics two or more times before the age of three, their risk of developing ADHD more than doubled.

The research, led by Dr. David Warner, a Mayo Clinic pediatric anesthesiologist, was prompted by similar research involving young animals.

“There started to be some papers published that suggested if you administered anesthesia to animals during development, it would cause some of the nerve cells in the brain to die, which would then lead to later changes in learning and behavior,” Warner told FoxNews.com.  “I and my colleagues had a real difficult time believing this would be true in children, so we tried to think of some way to look at this in people.”

Warner recalled the Mayo Clinic had done some research looking at the epidemiology of learning disorders in children born from 1976 to 1982 in Rochester, Minn.  Out of the 341 cases they reviewed, children with no anesthesia exposure or just a single exposure to anesthesia had ADHD at a rate of about 7.3 percent.  Children who had two or more exposures had ADHD at a rate of 17.9 percent. The researchers also tried to adjust for other risk factors, such as gestational age, sex, birth weight, and comorbid health conditions.

While the results are initially staggering, Warner cautioned that people should not to jump to conclusions.  Because the study was done retrospectively, the data does not necessarily indicate a causative relationship.

“What we’re trying to emphasize with this study is that we’re not proving anesthesia causes problems.  We really can’t say anything about what’s causing the findings we see.  But there is an association here,” Warner said. “When you put these results together with the animal studies that have been done, it makes us concerned.”

Though the team can’t definitively say why anesthesia would increase a child’s ADHD, they have a few theories after studying the animal research.

“What they understand from the animal studies so far, is that as your brain develops it normally goes through a process where some of the nerve cells die,” Warner said.  “In order for new connections to be made, old connections need to be abolished.  What appears to be happening in these animals is that exposure to anesthesia accelerates this process of nerves dying – dying prematurely appears to interfere with some of the connections that need to be made that are important for learning and memory.”

Even though their results are not sufficient enough to draw conclusions, Warner said there’s enough evidence for him and his team to continue to search for answers.  The next step would be for them to create an experimental study of their own.

“Now we need to do more studies in children to either confirm the findings we find or not,” Warner said.  “I would be very happy if someone were to refute our findings.  As an anesthetic pediatrician, this is not something I want to see.  We’re hoping this kind of research will stimulate more studies in both animals and kids so we know what’s going on if indeed anything is going on.”

“But we’re still several years away from having a more definitive answer,” he added.