"It might seem that if this was a problem, we would have noticed it by now, but that may not be true," says Flick. "The time lag between the event, the anesthesia exposure, and the outcome on development, may be years long so it would be quite difficult to connect those two things," he says.
The link was original suggested in the late 1990s when research in animals showed that animals that were put under with anesthesia many times showed brain cell death -- "regression of the brain, if you will," says Roizen.
Since then, further animal studies in rodents and monkeys consistently show that repeated exposure to anesthesia cause irreversible loss of brain cells and developmental issues.
In monkey models, even one episode of exposure to anesthesia during important periods of brain growth early in life resulted in deficiencies in memory and learning difficulties later," Roizen says.
"Really this points to how much we need more research," he says. "Because the data is very suggestive that this is a problem, but we don't know for sure. We also don't know if there is something protective we can give alongside the anesthetic to block this effect."